Very cool!
Please note that the HN community takes a rather strict approach when moderating comments that contribute noise to the conversation. "Nice article!" comments are routinely downvoted. As is sarcasm, witticisms, memes, references and other styles of comments that occur frequently but do not contribute to the discussion. It's a knowingly doomed attempt to hold back the flood of noise that covers Reddit.
I propose that "Very cool," "Thank you," and other pleasantries be upvoted. They are what you'd want a community to consist of: optimism.
I'll have to disagree with your characterization of HN. The site isn't here to serve you. It's much more interesting than that. You're a member of a community. I remember vividly what the site was like in the very early days. "Very cool!" type comments were there, alongside thoughtful comments about the relative merits of quicksort.
Pg said that empty-but-pleasant comments are fine, for what it's worth. I didn't mean to say that everyone should upvote them, but it's mistaken for them to be downvoted, or to call them out as examples of what not to write.
Comments like "Thanks for making this" are morale boosters. Keeping them (or at least not discouraging them) might encourage people to show more stuff they've made.
Imagine if there were 40 comments that all said "Cool" or "Nice work". Do you think they should all be upvoted? "Very cool" followed by how or why you think it's cool, or something else constructive, is worth reading. "Very cool" by itself is just a mindless blurting of emotion.
If you want to boost the author's morale, send them an email or message saying you like their work. No need to pollute the comment section here.
This has never happened. And it won't happen. We're worrying about the wrong things. It doesn't make sense to reply to "Coffee is good" by saying "Careful, you might drown in it."
A comment doesn't need to add anything. The sorting algorithm penalizes short comments. They end up at the bottom.
Imagine if there were forty comments that said variations of "Thank you." After you read the first one, you'd know immediately to stop reading. The sorting algorithm ensures you won't miss anything. Troll comments, perhaps, but not valuable ones.
Alternatively, you could read all forty comments. It would be about a hundred words in total.