Post History

This is a fun one. This is a bug, but it's also not something we can retroactively fix, so... [status-known-about], I guess?

We discovered when we ran the import for the new stuff from Ebooks that importing stuff into a category that's already in-use is... to put it succinctly... a really bad idea. It:

 * Runs over _every_ tag in the category doing post associations, instead of just the new tags;
 * Causes problems with voting by duplicating community-user records;
 * Tries to re-associate all existing posts with other posts based on the assumption that the Stack Exchange post ID is available, which it isn't for posts that have not just been imported.

We've mostly got away with this one; the number of posts imported was small, so the damage is limited mostly to a handful of posts that have things like this, as you've noticed. It's not practical to retroactively fix, unfortunately, but the number of posts affected is fortunately small.

We've worked out a fix for this in future using invisible temporary categories, so this doesn't affect our ability to import into existing categories going forward.