I think in that case I’d probably add an update to the comment. But downvoting yourself feels really honest somehow

But other people might make similar incorrect comments, better that your comment with the reply that makes a correction float to the top (for people who sort by upvotes). The best solution is probably editing if you have the time and upvoting the reply. Similarly I'll upvote something incorrect if I reply to it but downvote if I don't have the time to reply.