is hardly adding any value, whatsoever.
Yes but they are explicitly accounted for in the site docs/design/intent, from waaaay back:
Empty comments can be ok if they're positive. There's nothing wrong with submitting a comment saying just "Thanks." What we especially discourage are comments that are empty and negative—comments that are mere name-calling.
https://news.ycombinator.com/newswelcome.html
And pop up in moderation comments
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
> There's nothing wrong with submitting a comment saying just "Thanks."
I'm pretty sure they meant saying "Thanks." in response to another comment, not as a top-level comment reply to a Show HN.
Kind of like how you wouldn't bust into a restaurant and say a loud "Thanks." to the entire room, despite it being perfectly fine to say thanks in a restaurant.
You can see the this covered in the mod comments, toplevel positive fluff is fine. Most of it doesn't go anywhere (as in, it's not like these end up the top of the thread and collect fluffreplies) and are, at a minimum, not worth policing.