Note: Users that cause persistent disruption to harmonious editing or who are uncivil can be reported to Wikipedia:Administrators' noticeboard/Incidents.
There are relatively few difficult users, but they need to be avoided to stay focused on writing the encyclopedia, and not let petty squabbles cause frustrations and doubts about other, decent users. Vast numbers of users, rarely seen, are highly considerate and intelligent people. Only a few users are difficult, so they should be avoided to keep working with the nice guys. Avoiding those users also means avoiding some significant articles where they obsess and dwell.
Wikipedia has roughly 10 million registered users, so if the vast bulk of people were jerks, then every article would be totally trashed, and every user-page would be filled with warring insults added by everyone else. No, instead, most wiki-people are good, and it is just a "small group" of difficult users who cause most problems.
However, even a small percentage of 10 million users, is a considerable number of difficult users. Consequently, they are encountered every few days and even though rare, they know how to be difficult. They have a history of being difficult, so they've had a lot of practice, and know all the tricks to upsetting people.
A lot of difficult users act like Internet trolls: they bait and insult to get a reaction, and to see their victims suffer. However, if ignored, they lose interest when their victims escape, so they move on to find other victims. To avoid them, one solution is to stop participation for a few days or a week; trolls will fill-up the time by finding a new controversy to become involved in and may lose interest in old ones.
The illusion of "jerk-ipedia" is fostered when difficult users band together, as a sort of gang mentality. Even though they are few, when perhaps 5 people gang up and spew vitriol onto a new user, it gives the intense illusion, as one person concluded: "the inmates are running the asylum". They are not. Most people in charge are not nut-cases, not slowly insulting others. The vast majority of Wikipedia articles are written by normal people, with healthy attitudes, and common courtesy. Most of the 846 admins are well-mannered and grounded in reality, and the few unusual admins are generally removed, and quickly.
Wikipedia warns new users not to reveal personal information. Although they don't necessarily know where anyone lives, some difficult users find where you write. The problem of wiki-stalking involves tracing user-editing of various pages, along with determining a list of people you have contacted, by analyzing your access to user-talk pages. The real dangers:
Basically, you don't even need to be present at all to have a long set of problems thrust into each article you wrote, contacts to users you know and debates stating how wrong your opinions are (or rather, would be). Even though you never even entered the discussion, some users will predict your opinions (in writing) just to let others see how wrong you are about something you never said.
Many difficult users can be detected early by the off-balance actions that they employ: "where there's smoke there's fire". Remember, though, that users might just be copy-catting bad behavior, and also that first impressions of how people behave can be misleading. Look for multiple warning signs to find repeated patterns of behavior. Some signs:
Again, many difficult users have a lot of impact, so some new users might get goaded into bad behavior, in a copy-cat manner, and it takes a few combined actions to realize the behavior is a pattern of intentional, negative, and insulting actions by truly difficult users.
Of course, numerous Wikipedia editors have left in disgust at such petty, psycho behavior. However, remember, in general, when it comes to your "bad" wiki-reputation, no one really cares. It's a volunteer project, and most people are too busy to worry about wiki-reputations. If people really cared about that, then certainly all difficult users would have been banned for their reputations, many years ago, from the wiki-Solar System. But they haven't; instead, troublesome users are generally ignored, and so are their angry remarks about your wiki-reputation.
Most people have simply decided to ignore those difficult users and, also, ignore the veiled insults or other mud thrown at wiki-reputations. In general, people don't think about who is wrong or who is right, but rather, "Those guys sure argued a whole lot". Decent people won't believe angry remarks that others say about you. So it is not a real problem, like it might be in live social settings, where typically, insults must be backed by some real facts to convince others.
Similar to a legendary troll under the bridge, who waits and makes demands of travelers trying to cross the bridge, the difficult users tend to hang around some significant articles, knowing that certain people will want to change or correct part of the text. Just as the troll exerts power against those wanting to cross the bridge, the difficult users feel they have a "captive audience" in particular articles. Specific changes will be reverted and disallowed by them. Those articles should be avoided, abandoned, as areas of continual confrontation, at least for a few weeks.
Perhaps the most that can be done is to lodge a "POV dispute" on an article's talk-page, but not carry out a protracted debate, because the difficult users will likely escalate any rebellion to become wiki-stalking and hounding of their rivals. However, soon, some of those users will likely "archive" your comment topics (as being old topics) from the active talk-page, further denying your voice about the article. At any given time, there are well over 50,000 highly significant articles, so just visit some minor articles first, until those difficult users have lost interest in following. Then, later, try to improve some other significant article, which is not a battleground for such controversies.
Many difficult users have left within 2 years of joining Wikipedia, as they struggled to gain more power, but were continually ignored or rejected. Eventually, they snapped, and went out in "a blaze of glory" by insulting everything and everyone, until the admins reverted their hateful, final rants from the pages where they had cast their vicious parting remarks.
However, other less maniacal users have acted as "semi-trolls" with more balance, and remained years longer. One user thought the solution was to list every difficult user on his user-talk page, but that tends to merely anger them. Instead, just keep a private list, off-line from Wikipedia, so that when the names of difficult users re-appear, you can review their infamous antics of the past, and take evasive action.
Each veiled insult, or slur, against your wiki-reputation can be given an easy spin, with follow-on wording that focuses on a strongly positive view about each comment. Examples:
Although the glowing, positive terms might seem excessive, the effect is perfect. A dull veiled insult, obviously intended to scar your reputation (in writing), is reformed into a 100x times greater compliment, to all who later see the entry. Because of the hugely wonderful, over-the-top positive wording, those spins have a second benefit of laughing away the insults, which were not just undone, but thoroughly trounced, beaten down 100 times, by the overly-positive wording of the enthusiastic spin. The reason each spin can work so well, against the insults, is that, typically, an insulting remark must be mild (otherwise it becomes a vicious personal attack), so consequently the positive spin can easily claim a viewpoint 100x times the opposite, as an enormous compliment. The result: insults can always be reworded as a 100x better compliment. It's a guaranteed easy win, with a humorous spin 100x times funnier than the meager insults. Rather than having to re-read, each time, the negative wording of the insult, the text to be seen, each time, is the glowing positive view of the improvements (or other "great impact to the universe") that you have made.
You will have won, completely, and avoided the insulting words of the difficult users.
It might be tempting to try to reform the difficult users. A moderate amount of personal discussion, with those users, could be considered as beneficial to Wikipedia. However, Wikipedia is founded to write the encyclopedia, not provide cyber-counseling or psychiatric treatment to disturbed individuals, and not to convert the hearts of hateful people to become humanized. It would be unethical to use Wikipedia outside the stated policies of the Wikimedia Foundation, even when following good intentions. Perhaps the most you can do is say a prayer, or otherwise, counsel with them outside the scope of Wikipedia, but always protect your identity: "Beyond this point, there be demons".
Many difficult users tend to block progress, and some simply want to stop others from writing articles. Confrontations with them can be utterly demoralizing and make people want to abandon Wikipedia. Again, the interactions with difficult users can be so unpleasant that many people have quit. Consequently, because of that focus, the simple act of ignoring troublesome users, and moving on to improve another article, constitutes a total victory over their attempts to block other people from working on articles.
Try to tune out the difficult users and, instead, always remember the millions of other people who are helping to improve Wikipedia. Mustering the renewed enthusiasm, to improve even one more article, is the ultimate win.