Community wiki is one of the most misunderstood and misused features of the SE network. The original purpose of CW was to enable collaboration on a post, it reduces the reputation needed for editing and results in collective authorship of the post instead of having an individual author.
But that is not how it is used most of the time. If a user that is completely new to SE would look at CW posts, I strongly doubt that they could make any sense of why certain posts are CW. There is nothing "wiki" or "community" about those posts, and that is because in most cases CW is misused as a reputation denial mechanism. And while part of this misuse is by the communities, a very large part is actually by SE itself. There are several automatic conversions to community wiki, and most of them are misusing CW for the reputation denial side-effect.
The automatic community wiki conversions are also a rather blunt instrument, and they often affect users that didn't do anything wrong. A user that substantially updates their posts over a long time frame will hit the auto-CW at some point, and not that many users know that they can flag for a moderator to remove it again. Also users that provide a good answer to a too popular question are likely to get hit by the auto-CW that triggers when too many answers are posted.
The automatic conversions to community wiki are fundamentally flawed. They're not very good at achieving their actual purpose, they are likely to hit innocent users, and they contribute to the confusion about what community wiki is actually meant for. I'm proposing to get rid of all of them and replace them with better alternatives.
Automatic conversion after 10 edits:
The purpose of this is to discourage excessive bumping of your own posts in order to gain more reputation. One major problem with this is that for a new user this is just terribly confusing, suddenly they don't gain any reputation for that post anymore but they aren't told what they did actually wrong.
I'd replace this with two mechanisms. First, users should get a warning once they edited a post more often than x times, the warning should remind them to make only substantial edits and to avoid excessive bumping. This should educate users about the issue, and it should be sufficient to deal with users that bump excessively out of ignorance.
To deal with users that intentionally abuse editing to bump their posts excessively I would create an automatic flag for moderators. At the current threshold of 10 edits this would likely be excessively noisy on larger sites, but I think this could be fixed by making the criteria a bit more intelligent:
- Ignore the first post in x months above 10 edits. The harm is minimal to non-existent if a user hits the threshold only very rarely. These cases are also likely to be harmless.
- Add a time component. If a user substantially edits a post over a long time frame this is likely to be harmless.
There are certainly ways to abuse editing and avoid these flags, but I think we can rely on the community to notice users that abuse this on a large scale.
Automatic conversion after 30 answers:
Nobody reads the second page of answers anyway. If having that many answers is so harmful that we currently punish all users, even those that posted excellent answers early, then we should simply add a hard limit to the number of answers. Questions with multiple pages of answers are very problematic and time-consuming to moderate, the later answers tend to be rather crappy or duplicate answers, and not enough people see and moderate them because they are on the second or third page.
Automatic conversion after 5 users edited the post:
This is the one mechanism that is not primarily used for the reputation denial. But it is still a confusing mechanism that doesn't really serve any useful purpose. I don't think anyone would miss it if it were simply removed.
Manual CW for certain questions:
Community wiki was used a lot to avoid giving out reputation for certain types of more subjective questions. This is strongly discouraged now, but some sites continue this usage.
This is also confusing for new users as they get the impression that reputation denial is the primary purpose of community wiki.
I'd remove the ability to CW questions entirely, it is used pretty much exclusively for the reputation denial. To support the sites that still use CW this way I'd propose to add a differently named mechanism with the only purpose to remove any reputation gain from the question and its answers. This would avoid confusion for new users, and it would enable some useful corrections to the behavior like e.g. removing the reputation gain retroactively.