Isn't a trademark always tied to its respective business domain?

Yes, but those "classes" can be quite wide, there is for example no way they could trademark it for "Class 9: Computer and software products and electrical and scientific products."

Wait until you find out about "apple" and "windows".

Apple and windows are trademarks for software. You would be unable to get the trademark "Apple" for a company selling fruit, or "windows" for a window fitter, and neither could Apple or Microsoft.

𝕏 is a pre-existing symbol used by, and part of a standard character set for, software. You could probably get a trademark on it for a company selling apples, but I highly doubt you could for a software company.

> 𝕏 is a pre-existing symbol used by

"used by" is pretty debatable. Its a fairly obscure character. I don't think being in unicode by itself is sufficient enough to count.

There is also https://www.x.org/ which seems quite slow. I wonder if it's receiving more traffic than usually..

> its respective business domain

Or to any number of business domains. See the trademark registration for "Wagatha Christie":

https://trademarks.ipo.gov.uk/ipo-tmcase/page/Results/1/UK00...

I don't see a problem with this, it's a generic character used in mathematics. If nobody trademarked it before, it shouldn't cause any issues. If using greek letters like λ in brands is not a problem, then this should fly too.

They could also apply for multiple trademarks with small additions if they launch a new product:

𝕏ₚₐᵧ

Trademarks are against a "class", these can be quite wide. They would clearly want to own that exact symbol for "Class 9: Computer and software products and electrical and scientific products."

Unicode already contains exactly it, it's a mathematical/scientific symbol, even if they did get the trademark in that category (which I doubt) they will never be able to enforce it. With trade marks, if you don't successfully protect them, you loose them.

It’s totally enforceable. It’s a trademark. Who else is doing business with the Unicode doublestruck X?

I think this would seriously confuse his core audience, so I doubt that’s the intention. Then again, I think rebranding Twitter to X is a terrible idea, so what do I know.

It is a problem, because if theoretically Musk were to trademark that character (improbable), Unicode would likely be forced to remove that character and break every instance of it across the internet. Not to mention that anybody using that symbol, which already has an established meaning in mathematics, would be infringing on that trademark.