Eh? Unless otherwise specified, corporations satisfy the definition of a person across all federal laws per 1 USC §1, which reads: "the words “person” and “whoever” include corporations, companies, associations, firms, partnerships, societies, and joint stock companies, as well as individuals"

That 1 USC §1 is not a typo: this copy appears in the first section of the first title of US code, on disambiguating common terms used in law.

The supreme court says a lot of things.

Just because Supreme court said it doesn't mean they aren't heavily biased.

This is exactly the simplistic framing the person you replied to is talking about. So let's take an absurd extreme. The government designates a 1x1 mile "free speech zone" in the middle of Wyoming and says you're not allowed to speak anywhere else. You have the same amount of free speech as you did before, right?

Another extreme, let's say the government declared that you may speak freely but only by filling out a web form routed to Dave. Great guy. I mean they haven't technically taken away your right to speak? And someone will hear what you say.

Both of these would he flagrant violations of 1A as I'm sure you'd agree. But what this means is that implicit to 1A the government has limits on how many places it can deny you speech and limits on how much they can deny you an audience. And you can't hide behind the "well it's just divestiture not a ban" because the courts aren't blind to POSIWID.

So the more nuanced question is does banning TikTok meaningfully affect the ability of Americans to speak. And I think because of how large they are you could answer yes to this question. Americans know exactly what they're signing up for with their TT accounts and want to post there. TikTok but owned by an American would be legal so the platform itself isn't the issue. And saying TT can't operate in the US and actively preventing Americans from accessing it are two very different actions.