Notify of posts made while you were posting

[dangerine]

We briefly used SMP when we first started our forum and had a very popular hack I haven't been able to find for vB (if you know of something similar, link please!)

If there was a new post to a thread submitted while you were typing yours, on hitting Submit you'd get sent to the Preview screen with a note at the top that said, "There have been X new posts to this thread" and at the bottom of the screen (where the last bunch of posts are), you could read them. The getting to read the new posts was handy, but the really important thing was knowing someone was posting while you were. We had WAY fewer double-posts and 18 people saying the same thing in a row.

For very busy threads and ESPECIALLY for Q & A threads, this was SO useful. My users have been clamouring for it back, but I can't find anything like it for vB. Please, oh better coders than I, any ideas on how to add a 'While You Were Posting' mod?