[crazygringo]

Not terrible at all.

It's super-useful to temporarily comment out a bit of code, and then to comment out a larger block surrounding it. Especially when debugging.

Sadly I've never used a language that supported that.

[wavemode]

Common Lisp has nested comments with the #| reader macro.

https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node191.html