Is there a way to "mark all topics read"?
Well, thanks for letting me know!
JK, I don't think it's going to get into the next release - some people have been working on new forums stuff but they're slow and not interacting much with core drupal developers. A mark as read button is probably something we could do ourselves though.
but threads are marked "new" when unread, and when you read them they lose that mark. is that not the same idea, or am i missing it entirely?
phpbb based forums (like the backup forum) have a button to 'mark all threads read' so if you've read everything of interest to you in a forum, or have been away for a bit and want the 'new threads' messages to start from scratch you can make them all appear as if you've read them already



Can comment on articles and discussions
nope
drupal (the site software) is better than the old setup in many ways, but standard forum functionality isn't one of them
fingers crossed the next update of drupal should have much better forum features, here's hoping ...