The binary "is spam" thing seems like a non-issue, unless I'm misunderstanding something. In Python you can easily implement Boolean attributes using predicates without breaking the API, like so:

    @property
    def is_spam(self) -> bool:
       return self._comment_check in {"true", "blatant"}

Then you can simply add another predicate to support the blatant case:

    @property
    def is_blatant_spam(self) -> bool:
       return self._comment_check == "blatant"