It might be nice to have a little icon next to threads that have not been viewed by the user yet, or at least when it is the first time display for that user.

you mean you want us to store who looks at what threads o.O
lol

/me thinks

say we have 25k threads and 1k users... that's 2.5M rows right there!

lol

could be done i guess though

well you could have a way to display/sort thread created date rather than just recent post date

mmmm like create some sort of "activity" metric based on number of recent posts, how recent, etc?

or by like post count?

Doesn't new threads and posts highlight anyway?
Mine does..

same here. could be a browser auto feature though prob

It's not a browser auto feature, it is because the link changes every time a new post is made. That ?p= in the link is the timestamp that always updates upon posting.

mhmmm the ?p is specifically to make the links update ;)