[mercer]

Yeah, when your karma is high enough. I don't know what the amount is that leads to downvote enlightenment though.

[eric_h]

I believe it is 1000.

[falsedan]

It's less than 1Mk (one megakarma).

[JetSpiegel]

It's 1 kk (kilokarma).

[falsedan]

It's also less than that, but more than 40 dak (decakarma)

[joncrocks]

It's around the 500 mark at the moment for comment downvoting I believe.