[Remark: Title says "Posts" meaning "Comments", not "Discussions"] [Title edited by Peter :)]
I wonder if people think it might be better to show discussion comments with the oldest comments at the top. In many cases, people might be responding to earlier comments and it's confusing to figure this out in the current order. Also, it would be nice to be able to quote previous comments in a subsequent comment, or comment directly to an earlier comment (similar to the format of Reddit and math.stackexchange.com).
The highly-successful AoPS forum uses this format, as have several other similar math community sites.