[qingcharles]

I'm not sure. There was a short period when you could register one letter dotcoms before about 1994. He's owned it since forever that I know of. His first company was called X, which became PayPal.

I spent a long time in the mid-90s trying to persuade INTERNIC to let me register b.com.

[contingencies]

Shame. That would have made a great Chinese porn site. https://en.wiktionary.org/wiki/%e5%b1%84

[qingcharles]

I'm pretty certain you can register one-letter IDN .coms. I registered a bunch the day the IDN system went live, and I had no idea what characters I was registering or what they meant and I later let them all lapse.

[plorg]

See about a dozen comments in this thread, PayPal owned it post-acquisition until 2017 when Musk bought it back.