Reading troll comments has negative utility. Replying to a troll means causing that loss of utility to each reader who wants to read the reply (times the probability that they read the troll when reading the reply)

That's exactly the kind of consideration that should lead people to downvote responses to "trolls." If you think someone is stupidly "feeding trolls," you should downvote them.

It seems that E.Y. is miffed that readers aren't punishing troll feeders enough and that he's personally limited to a single downvote. As an end-run around this sad limitation, he seeks to multiply his downvote by 6 by instituting an automatic penalty for this class of downvotable comment.

Nothing is so outrageously bad about troll feeding that it can't be controlled by the normal means of karma allocation. The bottom line is that readers simply don't mind troll feeding as much as E.Y. minds it; otherwise they'd penalize it more by downvotes. E.Y. is trying to become more of an autocrat.