Also on a related note, I created a Greasemonkey script that allows you to navigate through the comments chronologically, using the right and left arrow keys. It helps with the problem that, once a thread becomes mature, it's hard to find the latest comments that were added.
It searches for specific usernames in a comment thread (replicating the ctrl+f 'by $username' trick that stopped working when the comment-header syntax changed to hide comment karma), then scrolls to the next result every time you re-click it. You choose the usernames to search for by editing the query variable in the bookmarklet.
