Elon Musk also did own x.com in the 1990s. [1] It was sold, but he repurchased it several years ago and left the page to resolve to a simple "x" index. [2] This usage was before Microsoft's 2003 registration.

[1] https://web.archive.org/web/19991114130555/http://x.com/mana...

[2] https://web.archive.org/web/20230401142845/http://x.com/