Intro:  

For the most part of my experience on Deviantart has been a good one so far. While I may have the intention of learning about art on this site and making friends, I have learned far more about human psychology than I ever thought I would, through the debates, comment threads and experiences I've had with trolls. I am fortunate enough not to have been directly targeted by trolls, but a few of my friends, including those closest to me, have been the victims of harassment by trolls.

I have made this article to help my fellow Deviants cope with these trolls in a positive manner.

In order to understand how to deal with trolls, one must first understand what a troll actually is...

  Troll Classification:  

What is a "troll"? Some would argue that merely posting provocative content is trolling, but that content can be the voicing of genuine but controversial opinions, so clearly that isn't the case. Trolls are defined by being those who post provocative content with clear malicious intent.
 
I have decided to create a 'Type' system to help classify and identify the trolls encountered on Deviantart.

Type 0: This is a person mistaken for being a troll. A false alarm; someone simply perceived as being a troll through a misunderstanding. They are genuine deviants/artists who have just made a mistake, that's all. They may have been looking for bases to practice artwork, and copied from someone (and be mistaken for an art thief) thinking it was a base. They may not understand the rules of copyright, or be confused as to how crediting works. They could be too young to have been taught this stuff.
They may be angry or upset when confronted (which can seem like troll-like behaviour at first), but in the end will do the right thing, or try to make amends. They are not a troll (or at least not intentionally).

Type 1: This is a person who appears to be trolling, but are actually trying to argue a point because they truly believe they are doing the right thing. In other words, they're not a troll, they just have strong opinions. They might be policing Deviantart for artwork they disagree with ethically or aesethically. They may be stubborn to accept opinions or facts that clash with their own. Of course, a person arguing valid points isn't a troll, but someone only classifies as a Type 1 troll if, and only if, they become insulting or mean in their comments. These types of troll usually only post harsh comments, and aren't the kind that would steal artwork. However, they may be guilty of spamming. They can be reasoned with, but it may take time and patience to explain things and to get them to come to their senses.

Type 1.5: This sort of person is almost a troll. They post intentionally disruptive or controversial things, but they are still pleasant to a large degree and normal conversation can be had with them. These 'almost trolls' are more commonly referred to as shitposters. They may seem scary or bad at first but they're actually harmless. 

Type 2: This type of troll is a real troll, with possible motives such as revenge, racism, or religion. They may steal artwork in revenge or steal and edit it, they might harass people or spam them, or preach some sort of hateful messages. A delicate and psychological approach is recommended when dealing with them. They may be reasoned with, but it will be difficult.

Type 3: This is the worst kind of troll. Most likely sadistic in nature and narcissistic. Their motive for trolling is simply to cause trouble and hurt people's feelings for their own entertainment. They may repeatedly comment harshly on many people's pages, steal artwork, edit it, edit screenshots, falsely report people and when confronted say nothing or reply with meaningless comebacks or extremely inappropriate comments. They're the really malicious kind of troll.

Type 4: This goes beyond mere trolling. Type 4's are basically criminals, hackers, pedos, and any other person guilty of serious illicit activity. If you encounter one, go to the staff immediately about it and report them. You may also wish to go to the police or authorities about them.

  Before you take any action against a Troll:  

Before you decide to intervene, think of the consequences of intervention. Decide whether or not you are ready to take on the troll in question. 

IF YOU DON'T FEEL READY TO TAKE ON A TROLL: Tell someone else in your online community about the troll (preferably in a way that avoids linking them, as any comments you do this in will turn up in the troll's Mentions in their Notifications) and let someone else handle it in that case. If the troll is giving you a lot of harassment, report them.

IN ORDER TO TAKE ON A TROLL: You must be ready for the troll to lash out at you. You may need to empathise with the troll (or at least pretend to). You must be mature and logical in your comments to them and maintain the moral high ground. And do not, under any circumstances, brag about having the moral high ground. That will only make things worse.

Do not try to take on a troll if you feel your emotions will get in the way. You will only feel hurt if you try to deal with them in an emotional state. Tell someone else in your online community about the troll and let someone else handle it in that case. 

  Dealing with Trolls:  

Type 0: The False Alarm

(Not technically a troll, but can be mistaken for one.)

They may act out, swear, be angry or upset, but this is only because they are confused, upset and scared. They should be approached with a gentle, honest and kind attitude. Be mature.
Find out why they did what they did, and try to find ways of resolving the issue. If they 'stole' someone's work, make them aware that it isn't right, but do so respectfully. Advise them to make a public apology if they are getting lots of hate, as it will help clear up these issues and show that they are a genuine deviant/artist who simply made a mistake.
You can ask them if they feel more comfortable noting you about things, rather than discussing things in comments. 
Type 0's are not really trolls.
It is not advisable to report them. Block if applicable.

Type 1: The Irritant

(Not technically a troll, but can be mistaken for one.)

They are trying to defend something, policing Deviantart for some cause they see as noble, or acting because they think it is the right thing to do, but are doing so in a way that is insulting or mean. 
They can be quite stubborn, but ultimately, with a clear, concise approach, they can be convinced to stop doing what they're doing, or at least to back off and calm down.
When dealing with them it is recommended you bring emotion out of the equation, and that you think as logically as you can. This will make reasoning with them much easier, and make your arguments more convincing. 

NB: Please note that a person making a series of valid arguments in a civilised way is not a troll. 

It is not advisable to report them. Block if applicable.

Type 1.5: The Shitposter

(Not technically a troll, but can be a bit offensive and therefore can be mistaken for one.)

They are almost trolls, but not quite. They're merely shitposting, which is to say that they're intentionally causing disruption, but in a way that is still acceptable or within the rules. They can be easily reasoned with and are often more polite than they may first seem. 

It is not advisable to report them. Block if applicable.

Type 2: The Lesser Troll

(A real troll.)

This kind of troll has lost some part of their rationality and their actions are mostly driven by emotion. As with type 1, approaching them with a calm logical attitude is best. Try to make them see the error of their ways. Let them know that you're not trying to antagonise them and that you just want to help them. Be patient as reasoning with them may take some time.

If what they're doing is intentionally hurtful and malicious or if they are spreading rumours or lies about other deviants spitefully, then it is recommended that you report them if they do not stop what they are doing within a few days.

Type 3: The Greater Troll

(A real troll.)

They cannot be reasoned with. They are only trolling for their own sick entertainment. Try to figure out if they are actually a Type 0, and make sure they're not just a confused deviant/artist.
Once you know for certain that they are a Type 3 troll, politely tell them that what they're doing is wrong, but do not feed the troll. After you have let them know that what they're doing is wrong, then report them immediately. They may start new accounts, but in most cases they'll eventually get bored and give up.

Type 4: Criminal

Type 4: They're beyond the level of trolling. Type 4's are criminals, hackers, pedos, and any other person guilty of serious illicit activity. Go to the staff immediately about it and report them. You may also wish to go to the police or authorities about them.

  Summary:  

Merely posting provocative content can be the voicing of genuine but controversial opinions or shitposting.

Trolls are defined by being those who post it with malicious intent. 

Type 2: Lesser Troll - A deviant who is a troll, but can still be reasoned with. 
Type 3: Greater Troll - A deviant who is a troll, and can not be reasoned with.
Type 4: Criminal - A deviant who is beyond being a mere troll, and should be reported to the staff or the police.

 Extra Tips for Dealing with Trolls:  

• As most trolls (and humans for that matter) are inherently narcissistic, appeal to their emotions. Let them know that they are a smart person, and that they are better than what they're currently doing. Make them feel good about making the right choice, rather than it feeling like a punishment.
• Checking the 'troll' in question's Activity page is a great way of finding out whether they're actually trolling or just confused. 
• Do not react emotionally and antagonise them, no matter how tempting it may be, unless you know you can handle the consequences.
• If they have their Activity hidden however, do not assume that they are a troll. Many people hide their activity simply for privacy reasons.
• If the troll starts making death threats or inappropriate comments of a violent or sexual nature, report them immediately.
• Someone disagreeing with someone else, and someone trolling someone else, are not the same thing at all. Be able to recognise the difference before intervening with an argument.
• Someone making valid points or arguments on your more controversial deviations is not a troll.