We've got your reply, which says it's not taboo and is actually common (not contradictory, lots of taboo things are common). And then we've got the other reply, which says it's not taboo because the idea is so ridiculous (implied "You'd have to be an idiot to believe it, and recognising that someone is an idiot isn't establishing a taboo").

I don't know whether it's past the mark enough to be considered a "taboo" yet, but the other comment replying to him is certainly treating it as taboo. I would note that many, many other people particularly in academia/important society act the same way as the other commenter. I'd also note I have felt strong social pressure to not hold the beliefs I hold about LLM's capacity for reasoning, including actually losing meaningful social status.

Probably worth remembering that different subcultures have different taboos.