I've also noticed that very obviously LLM-generated comments are called out, and the community tends to agree, but those that have any plausible deniability are given far too much leniency, and people will over-index on the guidelines to give them the benefit of the doubt.
I don't think a captcha is the solution, as it'll degrade conversation by an OOM though.
You can run temporary unsigned extensions for development purposes, but they are removed after 24 hours or whenever you quit Safari, which would make using it daily a non-starter.