I know a PM system is on the drawing board, but as a lighter-weight alternative (or addition), would it be possible to have a way to flag a post or thread for another user's attention?
For instance, if I'm posting in a thread where someone posted 6 months ago saying they were working on something. They've never come back to post it, but they're still active elsewhere on the forums. I could hit a "Notify poster" button on their last post, and they'd get a little (dismissable) indicator somewhere to remind them to look back at that thread. Or they could just dismiss it if they aren't interested.
Another situation would be if I was posting (for example) in a thread about a rules question, and I want to flag it for Ravingdork's attention to get his opinion. He'd get the notification, and could either look at it or not, but he'd at least be made aware of it. You could limit it to notifying people who's handles you mention in your own post, to avoid just spamming everyone.
Anyone else think this might be useful? Or have any other use cases?