The problem is the automatic (huge) recurring upcharge when you go over the limit, which doesn't seem sensible. It's much more reasonable to just not let you go above 2 staff users until you upgrade, or to let you have them for some time and then automatically remove the most recent 2 staff users if you don't upgrade in time, or show you a prompt when you log in to the admin panel forcing you to either upgrade or remove 2 staff members. This is how almost any other company would do it.

If for some reason they don't want to do these reasonable things, at the very least the onus is on them to make you accept a big red confirmation prompt when adding a third staff user saying "Warning: This is a premium feature. Your plan will now be upgraded to the $99/month tier, and you'll be charged $99/month beginning on [date]. Accept / Deny". They don't even do this, though.

Without a doubt, some or many customers have gotten surprise charges due to this. Warning about it once via email 7 days in advance is a bare minimum; that email will inevitably be missed by many and they may be silently upcharged for months (unless there's also a blatant notice in the UI, in which case you're probably only on the hook for just one or two months; which is still pretty bad). And this is likely deliberate and perhaps even a specific strategy on their part. This is what the OP was trying to say and warn people about.

I agree with them that this is a shady practice. It's a startup / subscriber model dark pattern. It's not that far off from and in some ways even more deceptive than companies that rely on making most of their money from customers who forget to cancel during trials or discount periods.

This isn't some pay-by-resource-usage thing like AWS, where the responsibility largely and (usually) rightfully falls on you to examine pricing and anticipate or prevent big increases in your bill. It'll still happen to some customers, but when it does, it's (generally) not AWS being shady.

And it's not something like Cloudflare where going over the limit incurs some concrete additional cost for the company; the 2 staff member limit is completely artificial and arbitrary. It's perfectly reasonable to have as a limit to encourage upgrading, but it's not reasonable to have lying in wait as a potential trap to unknowingly, near-silently fall into.

Most users of Ghost probably do not expect anything like this behavior at all and probably have not used any other service that operates like this, so I expect some or many have been caught blind-sided.

And on top of that, the CEO had absolutely no justification to cancel their account out of the blue, and then (if I understand correctly) only give them access to their data after a social media outcry. It was blatantly done in retaliation and anger. Maybe the OP's initial tone was a little too hostile, but I probably would've had a similar emotional knee-jerk reaction shortly after I saw this and considered the impact to other unsuspecting users, and I think it's absolutely a shady business practice even if it's perhaps not "extremely" shady, as they stated.

Legally, the customer may or may not have any grounds, but ethically, I think the company and CEO are in the wrong, here.