I don't think I explained myself well enough in there, then. My apologies.
Let's say I created a thread about favorite restaurants. I post "I like One," but later edit it and add "and Two. I would be able to see the edit history because it's my post. You do the same thing, but I wouldn't be able to view the history because it's not my post.
I haven't used the vBulletin Post edit history in quite a while. However, its designed as a moderator tool in XenForo and shows exact dates, times, modifications, and who performed an edit. This isn't meant for a non-staff audience; but could most likely be accomplished via an add-on if you so wished on your forums.
BTW, if you're ever interested in how it works on vBulletin, I can provide you a test account on a vBulletin forum I administrate (no, I'm not the owner, haha).