MACLISP I can't really comment on as I don't know it and Wikipedia makes no mention of this, but yeah - MyPy is definitely an optionally-typed python code checker. It fits that category for both comment-based and in-language type hints, because it performs checks based on that info.
For Python itself though: if you have a syntactic element which does not change behavior in literally any way, whether present or absent and regardless of what it contains: sounds like a comment to me.
For Python itself though: if you have a syntactic element which does not change behavior in literally any way, whether present or absent and regardless of what it contains: sounds like a comment to me.