The best I can figure it is this: 'suspended' has a temporary sense, 'banned' has a permanent sense. While 'permanently banned' is a tautology, 'permanently suspended' is an oxymoron.

https://en.wiktionary.org/wiki/suspended

suspended = Caused to stop for a while; interrupted or delayed.

https://en.wiktionary.org/wiki/banned

banned = Forbidden; not allowed.

https://en.wiktionary.org/wiki/oxymoron

oxymoron = A figure of speech in which two words or phrases with opposing meanings are used together intentionally for effect.

https://en.wiktionary.org/wiki/tautology

tautology = Redundant use of words

On the other hand 'banned for [duration]' and 'temporary ban' have definitely been in use for a long time, which I personally have never thought seems wrong. If those uses are in play, 'permanently banned' can actually be motivated for disambiguation.

And I would suggest '[permanent] suspension' may have connotations of a statement about reversibility. 'We have the ability to reverse this action [but we intend not to exercise that ability, ever].'

As a native speaker, it's probably a distinction without a difference. Both sound more harsh than regular suspension and both sound less harsh than permanently banned. Neither one tells you exactly what they've done in terms of the amount of effort required to re-instate him if they change their mind. Both signal that they're unlikely to change their minds any time soon.

With a physical location, "banned" sometimes implies they've been declared a persona non grata, and the police will be called if they return. Clearly that doesn't apply to an online platform.

In practice they effectively mean the same thing. I suspect they're going with "permanently suspended" now because they want to avoid people using phrases like they "banned free speech" or something similar to that.

"permanently suspended free speech" doesn't really sound much different than "banned free speech".

I can't really see this being a big deal, Bannon's got enough wealth to make his own website.

To me, "suspending" sounds like something you do to accounts, and "banning" sounds more like something you do to people. In practice they're often interchangeable.

I agree. Also note that for something like a Youtube account there are records associated (e.g. media files, logs, followers) which "suspending" could imply the operator has not deleted, whereas "banning" seems more narrowly focused on taking away the communication privileges from user in question.

As a native speaker, I've seen it too, and it's just wrong.

If you suspended someone and then said 'we're making your suspension permanent', it sounds like a 'cute'/think-you're-on-a-soap-opera way of saying 'you're now fired/expelled(/as applicable)'. Suspensions end. Even a suspension bridge for example is alluding to some temporal aspect, the natural outcome (gravity having its way) would be different.

Suspend means to literally hold up above the ground. A suspension bridge is called that because something is "above" it holding it up.

Yes. And when that thing ceases to hold it up, it will come crashing down.

They mean the same thing; it’s just a choice of words.

I think it is for emphasis and for clarity. It is to clarify that the ban isn't temporary. A ban could be revoked or it could have a time limit. Permanent means it can't be reverted. I wonder if 'suspended' might also link to the wording within their ToS, so that's why they use ban vs suspended.