To be clear, I didn't downvote their comment — I don't think it warranted it — I'm just saying I can sympathise with the argument that a comment that doesn't add anything useful to the discussion is a fair target for a downvote.

Saying "But what about x?" when you yourself provide a link that says that X is a non-issue doesn't make for an engaging discussion. "But what about x? This link suggests it's not a problem but I think it is because of y" does make for an engaging discussion, even if y is seemingly nonsense.