Talking about the general pattern, not this case in particular: I disagree. A downvote is a signal, "fewer comments like this one please". Sometimes it's obvio

Talking about the general pattern, not this case in particular: I disagree. A downvote is a signal, "fewer comments like this one please". Sometimes it's obvious what that means, but sometimes it's not. In that case it's perfectly reasonable to ask, what was it about my comment that you disliked? A feedback signal is only useful if understood, and sometimes to be understood it needs clarifying.