[AsyncAwait]

It has nothing to do with being kind. It has a lot do do with contributing to the discussion with something useful. Just asserting things without any evidence is not useful and thus downvoted to make more room for more useful comments nearer where people would see them, that's all.

[tpeo]

I disagree that a comment has to be sourced to be a contribution to the discussion. Whether or not something can be a contribution depends entirely on what people expect from comments. If all I expect is to have a little bit of thought, it doesn't really need to pack on citations, and even a question might suffice.

Which might sound dilletante-ish, but isn't really out of place for anyone reading a pop-sci article on animal cognition during a Saturday evening, on their spare time.

As for downvoting or upvoting, I've never seen any actual evidence that either does anything useful.

[AsyncAwait]

There's a difference between a comment stating an opinion having no citations, (I think that...) and one supposedly stating facts, (You cannot have...). At least if we want HN to maintain a higher quality of discussion than 4chan.