In addition to the highlighting comments made by the question owner (as described in a recent blog post), I think it would be a good idea to highlight comments left by the author of the answer being commented on.

This way, the conversation between asker and answerer is more defined/obvious.

Edit: This is an edit to bring this to the site owners attention again - It would help people like me with bad eyesight to track down their comments. I originally opposed the questioner highlighting, but experience has shown me that I was wrong, and I think that answerer highlighting of comments would be very useful.