I hope I’m not alone in finding it utterly ridiculous that a company can literally hold rights over a single letter.

Keep in mind that it's in a particular context. It seems a bit ridiculous as a headline, but if they were actively using the branding, it might not seem so ridiculous: imagine Facebook (I will not call them Meta) is already operating a social media site for posting short thoughts called X with the TLD social (hypothetically). And they've been operating it as X for 10 years. Then Elon does this. Clearly Facebook has a suit because that's straight-up infringement.

This is a little more hazy because Facebook isn't actively using their X trademark, and it's not exactly the same as Twitter. But they do hold the rights to it (as far as I can tell from the one tweet (xeet?) about it). And it's not (quite) as ridiculous as it sounds.

Also,

Twitter auto-replied to Insider's request for comment with a message saying that the communications department would get back to us soon.

Is this a euphemism for the poop emoji??

A “tweet” is now an “x”. So somebody x’d that x was already trademarked. Dumb as fuck. My 8 year old is even over here calling Elon a dumbass.

So instead of tweeting something do they now "X it out"?

Yes. And for Twitter videos they are now “x-videos”. Should help draw traffic to the site.

so, I'm just going out on a limb here, but instead of liking something, do you now "x-rate" something?