Interesting, I never considered that voting would be so sensitive to these sorts of variables. Although this could have some effect, I'll be the first to admit my ability to communicate through this medium needs some serious work.

I don't see how a comment's upvote-worthiness changes with time of day.

> comment's upvote-worthiness changes with time of day

You have fewer people around to upvote you.

Another issue is that if you read HN through the RSS feed, you will almost always be commenting on older submissions.