Suicide by sysop
If one has inherently decided to leave, but somehow knows that one would not have the strength to stay away, one enforces ones own decision by allowing oneself to collide with one or more sysops, preferably very restrictive or overworked ones, to ensure one gets banned. By that way, one might draw a good amount of attention, disrupts the work of the wiki, may get a feeling of revenge and eventually regret after one succeeded. From the outside, 'suicide by sysop' looks very much like vandalism.
The problem is, that this wiki concept is so attractive, that it gets easily addictive. Basically, co-operative work is a very inspiring, very human activity. But on the other hand, most wiki communities are not personal at all, only intellectual. People do not or rarely meet personally. They only interact on a highly abstract level. That leads to the problem type of Do you want to be Right or have meaningful Relationships?. On wikis with no personal meetings, it must lead to escalations of attempts 'to be right'. So, if one thinks on is 'right', but there are sufficient other people around who over-vote one with the 'wrong' decision, one gets not only frustrated but depressed and looses the emotional bond with the project. So one may leave the project, not without any outspoken frustration and negative prognosis for the future of the project and the remaining 'wrong doers'.
Now the next best step would be to go to another wiki, where 'better' people are. Inevitably one finds out, that those people are also not better. One can go further round to more wikis. Eventually one comes back to first wiki and collects a lot of laughter like: "He again! Didn't he say he would never come back and we would go down anyway?". That way, one has proven one self practically 'wrong'. A very painful experience for many dogmatists.
So, any person that confuses learning with collecting negative experiences learns from this, that they are actually addicted to something that 'causes' them lots of emotional pain. And since they could not make the problem (the wiki project or its 'wrong' people) go away, they try to make sure that they loose access to it, at least under the account name under which they received so much humiliation. Therefore this account needs to be banned, blocked for an infinite period without remedy. If one asks for a block of ones own account, it is not only another humiliation, but one might be able to get it unblocked later on. But after wreaking havoc, one will not get the account unblocked ever again. For the person committing 'suicide by sysop', the project is as valuable, as a collection of spirituous beverages for the alcoholic who wants to quit: they have no hesitation to smash them all into the dustbin on one day, looking for money to buy more on the next day.