Welcome to Librarium Online!
One thought just crossed my mind.
How about having an update icon of some sort.
Many times threads are updated by...well not spaming, but general wordsharing, and sometimes the threadstarter has something more important to share.
Like if I post in my own thread on a conversion or painting thread and just talk away it might not be all that interesting for the general public, but if I have posted new pics it might be.
Then all I would have to do would be to tick in the little box (or whatever) and the "real update" icon would appear beside the title in the forum.
Am I the only one who first read that as a tournament?
To your question, not too sure I understand it, but it seems like you'd be getting a feature to determine which posts are genuinely interesting, and which are just casual chatter, which, as we all know, is what one would regard as rather difficult for a machine, then again, I could be wrong about what you're asking.
Just my thoughts on the matter, now I'd best head off and let someone more qualified than I give a better answer.
Interesting idea. It'd have to be something associated with the first post, I'm guessing, but I think AFG is probably right in that it'd be something rather difficult to code. Or it might have to be a feature of vbulletin.
What would work that I've seen on other boards is to allow the user to actually change the title of his own thread. That way people can add something like "Updated Jan. 06". However, only mods can change titles. Maybe that's something that could be altered?
Here was the latest discussion.