In addition to the highlighting comments made by the question owner (as described <a href="http://blog.stackoverflow.com/2009/08/new-question-asker-features/">in a recent blog post</a>), 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.