This doesn't seem at all unlikely to me. I think we sometimes forget the ease (in terms of scale and cost) of standing up a massive astroturfing campaign.

That said, I don't think this particular comment has the flavor, tone, or message I'd expect, and it does seem to be a genuine HN poster.

You are absurdly naive if you think they’re incapable or unlikely to do such a thing. Half the comments and threads on this site are ads at this point.

I mean did you see the completely unironic thread where discussors were mentioning "$50 Tees" as the lowest acceptable end of quality?