Apologize if this has already been reported, but I couldn't find it in the first 5 or 6 pages of search results (after that they don't appear to be relevant).
1. Make a forum comment post with a typo. Bad fingers!
2. Go back and edit it. Click Preview before posting. Preview, looks good.
3. Click Post. Didn't change at all.
4. Huh? Edit again and Preview again before posting. Notice this time that while the preview updates, the text that shows up in the editor textarea below the preview isn't my edited text -- it's the original version. So, to edit - preview - post successfully, you have to copy your edited text from the preview area into the editor a second time before clicking Post.
Not earthshattering, but there it is.