Thanks for your support. However, your upvote didn't register (I still have 1 point on the comment). I noticed this sometimes happening with me recently, too. You can verify this by unvoting and looking at my karma in the profile not changing.

I think an equal number of upvotes and a downvotes/flags does this, too.

The test I suggested would reveal that, too.

Oooh, just tried upvoting this one and it looks like your karma stayed constant at 8301. Strange. I wonder if there's a limit to how much karma one account can give another through upvotes within a certain time period.