This is a question about etiquette and manners.
If you are answering or have answered a question and you disagree with something written in another answer, would you think it was ok to directly criticise that other answer in your own? For example, by editing your answer to include something like this:
"ProfRob's answer doesn't add much. In his answer he says x, y and z but I think he is wrong because of alpha, and beta."
Or, do you think that you should, at least initially, raise that objection as a comment on that answer, maybe with a downvote if you feel strongly, so that the other author knows they are being criticised and might perhaps resolve a misunderstanding or make a correction?
I would say the latter. I think whether the criticism is justified or not, some courtesy might be expected.
My problem with the former approach is that at best, it seems discourteous and will likely lead to an extended "exchange of views", and at worst it denies the right to respond if the other author is unaware of the edits being made in another answer.