Apple App Store allows Twitter’s “X” to break rule against one-letter apps

You’d have to define “discrimination”. Instead of using a singular word which is prone to misinterpretation, you should use more words to ask the deeper question that you’re vaguely referencing.

As it stands, your question doesn’t carry enough meaning itself to be meaningfully answered.

There are exceptions to every "rule," if you can even consider this a rule. When publishing to the App Store, the form says your app name must be between 2-255 characters, and it cannot match a name that already exists. So if you want to make an app listing called "Cloud," but that is taken, you may have to give it the name "Cloud — The Coolest Storage Solution" or something else.

However, if you have the trademark to an app name, you can contact Apple and they'll amend or delist the other app, and let you have it. This isn't even limited to Apple; I got a Twitter handle that was taken, but inactive, because I had the trademark.

Every single company will do this to cater to businesses, especially large businesses, because businesses often end up buying ads or onboarding lots of their employees or users onto the platform. That's just the nature of the game. Apple's App Store is certainly full of flaws, but making exceptions for large players is not unique to Apple or any platform.

Being discriminating about who you let use powerful things is a feature, not a bug. Using the word to imply predujice/unfairness is tiring and incorrect.

Legally? Ethically?

You’re always free to sue apple, assuming they haven’t forced you to sign a contract which allows them to deal with issues through binding arbitration in the jurisdiction of their choice.

They're discriminating against products that are least-likely to shovel them piles of cash, either to make the exception, or by operating on their platform and providing ad revenue...

I don't think it's /illegal/ discrimination. It's certainly obnoxious and I don't like it.

Apple isn't a democracy. They set rules that work for most people and are in their full right to choose differently for select vendors, including themselves.

In the case of Twitter, I'm sure they're themselves annoyed by Elon Musk's behavior, but they'd rather make small concessions, and make him shut up. For now.