> Purely from the content of his comment it doesn't seem like that's the case

You can't judge this by a single comment, since the whole point of this abuse is to make posts that are indistinguishable from grassroots comments, while advancing an agenda. To see the agenda you have to look at patterns across comments. You can begin to see that at https://news.ycombinator.com/posts?id=notamanager, but to really see it you have to look across multiple accounts.

> examples of moderation going the opposite way don't change anything about this particular instance

It changes the general conclusion some readers might otherwise jump to or fear. A single prominent case of moderation is enough to get a lot of sincere users worried about bias, and a counterexample or two is often enough to soothe those worries. I don't want any sincere Googlers on HN (which is basically all of the Googlers on HN) to feel like they're unwelcome or need to change their participation in the site. Anyone who likes both Google and HN should be mad that someone would tarnish the one by poisoning the other.

> Astroturfing would imply that he has a business motive

We can't read motive directly. We can only look at behavior patterns. I look at it as a duck-typing thing: if an account walks and quacks like a corporate propagandist, the name fits, regardless of who they work for or what their job title is.

Edit: unfortunately, internet users are far too quick to perceive other users this way, so the vast majority of the time we have to tell them that the name does not fit—to such an extent that this is in the site guidelines (https://news.ycombinator.com/newsguidelines.html) and perhaps the worst issue we face as moderators (https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme...) But still, sometimes it does fit, and dealing with such cases unequivocally is what enables us to make the contrary argument the rest of the time.

> This makes it seem like you're banning him for supporting his company with a valid argument

I'm not sure why it seems that way to you, but I appreciate your perspective and would be happy to hear more. I don't mean to imply that this is an easy issue. It's complex, and slippery to pin down in general. If you put the question as "is it a problem if someone is simply posting valid arguments in favor of their point of view?" it feels like the answer should be no. If you put it as "is it a problem if a specialist shows up with prepared talking points to influence any thread related to their agenda?", it feels like the answer should be yes. But those two things are almost the same, like a Russell conjugation. So how can we draw any line?

The best answer that I know is to look at all the evidence we have (some public, some not) and ask whether the account's behavior is consistent with the value of this site, which is intellectual curiosity. Single-purpose accounts tend not to be, so we don't allow those in general, especially when the single purpose is to advance the interests of some entity. When that pattern occurs repeatedly across multiple accounts, it fits the "does it walk like a duck" test for astroturfing, even if we don't know things like "is it paid" or "who they work for". Those questions aren't usually knowable and aren't intrinsically important. What matters is behavior on the site.