Knowing software development, probably it's not only Elon but a bunch of devs in Twitter and they can probably know that accounts are linked. Privacy on the web is really hard. Nostr by its nature is not good for privacy, because that's not the purpose of the protocol, you can be anon, but everything is public, it's the same problem with onchain bitcoin, censorship resistance and public open protocols are almost opposite of what is required for privacy. Myself personally I have no problem with that, my only concerns are: not having important personal data leaked if there's an hack in any platform, and I don't want people to be able to easily link my many different accounts, but I am very aware that if a gov or gov agency wants to track me they will, no matter what, and that applies to almost everyone.