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.