Notify of new posts to thread *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 it's already here, please link!)

It was really, really popular and great for busy threads - if there was a new post to a thread that was 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.

For very busy threads and ESPECIALLY for Q & A threads, this was SO useful. I'd love something like this for vB!