You say “They also now have the ability to edit tag descriptions in a wiki-like fashion”, but when someone does something stupid on Wikipedia other people can view the article history and restore old versions. Here it looks like regular users can’t do that?
My guess is that this is a temporary bug. The History page should allow users to see any previous revisions that were made, and should allow you to compare arbitrary revisions. You can see what it’s supposed to look like on LessWrong. With that, restoring previous versions should be pretty easy. I expect that bug will probably be fixed within a week or so, and until then it probably won’t be much of a problem.
My guess is that this is a temporary bug. The History page should allow users to see any previous revisions that were made, and should allow you to compare arbitrary revisions. You can see what it’s supposed to look like on LessWrong. With that, restoring previous versions should be pretty easy. I expect that bug will probably be fixed within a week or so, and until then it probably won’t be much of a problem.