Current talk pages are extremely unfriendly. I think they should be abandoned and replaced by more "natural" system of posting.
Article would contain: "Comment this article" and "View comments" links, with second present only if there are any. Occasional readers would be more willing to comment articles that way, with interface they are more familiar with.
Every comment would contain posting user name (or "Anonymous"), date, and "Reply" post.
Unlike K5, we don't want to keep posts forever, so some magic would be necessary to take care of old posts. Automatic expiration wouldn't be any good - some issues are resolved very quickly, others may stay for months.
I think that posts should have 3 states: current, old and deleted. Everyone should be able to move posts between current and old status, and sysops should be able to delete and undelete posts. Old posts should not be displayed in defalt "View comments", (some "Show also old comments" link should be provided), and deleted posts should be visible only to sysops.
Markup should be interpretted normally in posts, but some extra care should be taken that no formatting bomb will be placed in them.