I'm pretty sure I've seen dang or pg say that quick, low-effort comments that express enthusiasm for a comment or post are fine (whereas low-effort, drive-by dismissals are very much not fine). I've tried searching but it's not obvious what search terms would turn up such a comment.

But I hope my recollection about that is right. Yes we want comments to be substantive in general, but we don't want to be surly or even Grinch-like when someone is just expressing excitement and affirmation for someone else's contribution. I'm sure that's not what pg or dang would want here.