I was interested what the exact meaning of a “Middlebrow dismissal” is (non-native speaker). But I could only find the following in the HN guidelines which doesn’t seem to mention middlebrow dismissals nor does it seem to be applicable to the toplevel comment:

“Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something”

What exactly is a “middlebrow dismissal” and why would the toplevel comment be that?