New comments affect "recent" timestamp?

Hello there,

Just trying to sort out the configuration of my forum. It seems that someone posting a comment to a reply is currently not showing up as activity on the post - that is, if someone comments today on a two week old post or reply, for the purpose of 'recent' listings the thread will still be two weeks old. Relatedly, is there a way for commenting to be included in the "Last Reply" listing? We use commenting quite a bit on my forum and we're not capturing the true level of activity on many of our posts.

Thanks in advance!