Therefore, if anything can be done, ensure that it can be undone. Journal all (potentially damaging) changes to the site. Thus, any damage is done, it can be undone.
In this way, since there are more people willing to fix the site than damage it, damage can be quickly alleviated by the community. True, if you hold to ReversibleChange, even the fixes can be undone by anyone attacking the site, but as long as the undoings are undoable as well eventually the good guys will win. Patience is important.
But, certain things are irreversible, perhaps by design. Extra steps must be made to ensure the community generally accepts those permanent changes.
Also, the emotional costs of damage may be irreversible. Consider Wiki:DisagreeByDeleting and the ensuing flame wars, not to mention the shift in CommunityExpectations following the initial event. Lengthy arguments made possible by an inability to effect permanent change may make the participants extremely stressed and ready to leave.
The only way out of an EditWar is to not enter an edit war; remember, you will be here longer than they will. Just wait patiently until they stop caring, then delete it. However, sometimes EditWars become cosmic, and then you are in trouble. See EditWar for details.
The description above is pretty vague. An excellent example of ReversibleChange in action is the common feature of many wikis of an VersionHistory. Each page maintains some number of versions prior in its history so that if anyone came along and did damage, others could come along and revert the page to a previous clean state.
Another example on wikis of where ReversibleChange is difficult if not impossible is PageDeletion. Once the node in the page database has been deleted, the expectation is that it is really, truly gone, along with its page history. Consequently, care must be taken when implementing this such that no damage can be done by a small number of individuals, even if they are acting in GoodFaith.
Due to the complexity of rolling back (or failing to roll back) page deletion, many wikis have not implemented it. Thus, it is possible to spam their page database with insulting titles, for instance, or to preserve flame wars that one wishes to ForgiveAndForget. Meatball's DelayAction version of PageDeletion is one solution; WikiPedia uses HiddenPages based on AccessLevels; PlayingDead is another solution.
KuroShin employs its users to rate comments attached to articles. Some comments are considered beneath contempt. Consequently, a certain class of trusted users are given the ability to rate a comment 0. Any comment with an average less than 1 is hidden from everyone (including the author) except trusted users.
However, sometimes a trusted user abuses his or her power. To answer this, kuro5hin allows other trusted users to rate a comment back into visibility. All trusted users are also invited to "Review hidden comments" across the site via a link in their user preferences box that displays on every page load.
This is a remarkably effective system. Less than half a dozen messages are hidden a month, all deserve it, and never is one missed.
As mentioned above, on some wikis, edits can be reversed (if you can find a copy of the old content) but page creation can't be. When I last looked at MetaBaby, I found vandals had created many pages with obscene content and obscene names. In a wiki the content could be cleaned up (if someone cared enough to do it), but the page names would remain as a permanent blemish.
It seems to me that there should be a small group of people with the power to destroy a record from the database. i.e., the owners of a wiki should have the power to remove obscene content if the wiki's spirit is against that. -- IsaacRaway
But does it have to be immediate? The current page deletion mechanism allows deletion of pages -- and destruction of the entire page history -- but only when enough time has passed. -- AlexSchroeder