You don't have to look far through https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme... to see how many hours I've spent defending users accused of astroturfing and telling other users that they can't sling such accusations without evidence. That problem is actually far more serious than this one, in its corrosive effects. But the flip side is that it does occasionally happen that the evidence is so unequivocal that public banning is called for, and this is one of those cases.
Let people have multiple accounts for privacy if they want, but disallow multiple posts/comments/votes from the same person.
To pick a couple of famous names, I doubt that Alan Kay or Peter Norvig would have bothered with HN if we'd placed up-front demands on them. Countless experts have shown up here over the years to create accounts and share firsthand about what they know. Here's a recent example that sticks in my mind: https://news.ycombinator.com/item?id=22007115. It's particularly common for project creators or article authors to show up and comment on their work. We don't want to do anything to make that less likely.
HN is fortunate in that we're not under pressure to monetize users, squeeze more engagement out of them, or optimize them in any way. The factors that drive companies into corralling their users and eking information out of them don't apply here. The only thing we need to do is have HN be interesting. An open community, assuming it can be persuaded not to destroy itself, is more likely to be interesting.
Also, I can get an SMS over VIOP for cheap for a limited number of days. If I were an attacker the email/phone verification does nothing to stop me.
What's typical to see on Bookface are founders asking and answering questions about specific challenges, people launching their startups (that part is a bit overlappy with HN, but the discussions are smaller and I would say narrower), people looking to hire or get hired, people asking for intros, posts about apartments and offices for rent, announcements of events...that kind of thing.
This ban seems unfair, and if it is rooted in an anti-astroturfing policy, then that policy appears way too aggressive - no one wants HN to be a marketing site for mega-corps, but passionately defending one's favorite company shouldn't result in a ban. Also, the moderators have all the power, and accused none. While moderating is likely arduous and maybe even moribund, being a fanboy/AstroTurf-er especially one not behaving badly, isn't worthy of silencing/banning (that's my opinion).
The consumers of HN content have a healthy skepticism towards polarizing opinions, and as with all social media, have their guard up on what can be blindly trusted. This ban assumes your average HN-er cannot tell a fanboy apart from a neutral third party - which is not the case. Let opinions be, let the fanboys talk freely (as long as they're not impolite), and trust the HN audience to use their better judgement in drawing any conclusions. I don't think anyone assumes the top comment on any topic to be an endorsement by YC/HN, or it's users.