Reminds me of comments in MS batch files. I think there is just a program called REM (ie REMark, used to begin comments) which just ignores its arguments and immediately returns.

Clojure has that built-in and it’s great. Works wonders when testing things too: write a small test in a comment block and you can edit/evaluate a function then move to the comment and see the result immediately.

I always hesitate to return the commented expression or nil or '(:comment expr...)

Nonetheless comment macros are neat. Just like #_(ignored) in clojure or else.