I often post comments on HN, just to delete them 5 minutes later when I realize I don’t care to deal with the replies I’ll eventually get.
You have to be quick because if someone does reply, you can no longer delete your message.
However when I make comments here, I do it with the intention of reading what people have to say in response.
If I am making a comment with the intention to ignore the responses to it, then that’s a good signal for myself that what I am writing is likely not an appropriate comment for HN, and then delete it.
edit: you're right, there's a delete button.