Yep, there's some of my own comments I wish I could downvote for the same reason.

Really? This is a little surprising but only in a purely logistical sense. You don't tend to be in situations where that can be effective. Voting on your comments is more extreme than with most so whenever your comments form part of an unproductive conversation they already tend to be downvoted way below the threshold where less prominent users who draw less attention may only have reached -2 or -3. For this reason I suspect the current implementation handles this for you with requiring your noble self-sacrifice.

(Pardon me if I'm just being too literal and you meant "would wish to be able to downvote". The prominence and popularization factor is just what popped into my head following the "that would be redundant" thought.)

there's some of my own comments I wish I could downvote

Me too. And that was even a feature of the system, once upon a time. But I'm not bitter, no.