When a post in a thread has been modified, it appears in the recent questions area, but unless the question is closely followed, one cannot notice take note of what the changes are. This applies to both our own question (answer modifications aren't notified unless answerer comments to questioner) and questions that piques our interest, namely the ones we have favorited or provided an answer to.
Forum threads have an option to see "new posts since last visit", we need something like that here as well, or at least allow the user access to what the changes have been made in the thread.
Just post revisions is not enough, as I explained in my comment to Rebecca's answer. Large community wikis will have posts edited and answers added, and post revision logs do not help in that matter. I stand by my request and ask for a thread-level revision log.