Sure, everyone wants to "stop silly people replying to my comments by posting LLM-generated garbage", but rules are rules, so you should understand that by introducing a rule like the one you propose, you also automatically forbid discussions about "here's a weird trick to make LLM make stupid mistakes", or "biases of different LLMs" where people reply to each other which prompts they tried and what was the result. Obviously, that's not what you've meant (right?), and everyone understands that, so then it's a judgement call when this applies and when it doesn't, and, congratulations, you've made another stupid rule that no one follows "and that's ok".
"A guideline to refrain" seems better. Basically, this should be only slightly more tolerated than "let me google for you" replies: maybe not actively harmful, but rude. But, anyway, let's not be overly pretentious: who even reads all these guidelines (or rules for that matter)? Also, it is quite apparent, that the audience of HN is on average much less technical and "nerdy" than it was, say, 10 years ago, so, I guess, expect these answers to continue for quite some time and just deal with it.