I think the new post/unread tracking should only be done for subbed topics. People don't care about if there is a new post in every thread on the site, only the ones they are participating, or otherwise interested, in.
Ehh, sorta. I don't sub to every thread I post in, for good reason. Yes, posts move fast in RPs, but there are topics in Off Topic and RP discussion that don't drop off the first page so quickly. The NEW indicator is going to be useful there if you're just popping in to read and haven't found a reason to reply or sub yet.
Plus, this is also expected behavior for a forum. Obviously, the best behavior is going to be for subscriptions, but not everyone is going to have the same workflow.