[fmajid]

I'm seeing them right now. It seems to be rate limited based on your karma and how downvote-happy you are.

[m463]

I thought they disappeared sometimes. I thought it was if you commented in a thread?

[fsflover]

You can't downvote replies to your comments.

[LocalH]

I feel like downvoting also goes away after a comment has reached an age threshold, although I don't know what that threshold is.