Agreed, generally. I'd say comments are to express things the code itself cannot. More expressive languages can get by with good naming, some declarations, and clear idioms in many cases.

The most useful kind of comments are "why" comments, about why specific design trade-offs were chosen.

I mainly agree with you, but for something like that, "it's an AVL tree, look it up" is all it should need. Names and type declarations handle the rest.

If you want to dismiss me as "one of those" people that is anti-commenting, you're reading too much into what I said. You said, "it doesn't have comments!", I said "actually, it does, and they're even checked." The end.

In a more complex program, I'd add comments. How many, and the nature of the comments, depends on whether I was writing in something relatively low-level (like C) or something high-level (like Haskell, Erlang, or K).