The question Why was my question removed? is about a question that was deleted due to inactivity. There was discussion in the comments about community members casting undelete votes, and the post in question was finally undeleted (and remains so today).
Something appears to have changed though. I recently stumbled upon a different question that was also deleted by Community for inactivity, http://stackoverflow.com/questions/9010309/multiple-config-ru-files-and-nginx-passenger, and my initial reaction upon seeing it was to cast an undelete vote. But, since Community is a moderator, it said "A moderator has deleted this post and it cannot be undeleted".
So it seems like Community-deleted posts used to be undeletable, but no longer are. Was this an intentional change? It seems to me that since Community isn't a real moderator and inactivity is an imperfect hueristic for questions that should be deleted, then if someone cares enough to want to undelete one of these question that they ought to be able to try to get it undeleted. I've classified this as "bug", assuming this was the unintentional side-effect of another change, but I don't know, it might be considered "feature request".
Note: This quesiton was inspired by another question I just asked: Why was "Multiple config.ru files and nginx/passenger" deleted?