You're right, "congrats Jim" is an edge case, but so are the cases of "this sucks" or "commenter $foo doesn't like this" one-liners. That's a complete straw man

You're right, "congrats Jim" is an edge case, but so are the cases of "this sucks" or "commenter $foo doesn't like this" one-liners. That's a complete straw man. That stuff, as you note, already gets downvoted. Sam is targeting something else. The post is wading into the realm of "gratuitous" negativity (or "unwarranted", to use tptacek's equally slippery qualifier), which is not necessarily just brief, unsupported stuff. It's clear I think that Sam is getting at the disheartening feeling that entrepreneurs can experience when facing a withering critique of a nascent project. We want a supportive community but a withering critique can actually help ideas get better. This guideline is ill-defined and could be interpreted as "tone it down, folks". And paired with a move towards community moderation, it's all about interpretation. This guideline would be better redefined around clearer, more concrete criteria.