Discord has the perfect username system
(UPDATE: I swear I wrote this before the news that discord was changing their username system, ABSOLUTE PLONKERS)
People often get sad that they can't get the username they want.
I have no brand to care about, but still I'm a little sad that my github account has some numbers after the name. And it's an obscure name too, but there's just that many people that you're lucky if your name isn't already taken.
There are various strategies, intentionally or unintentionally taken by websites to address this problem.
Bird website and the dual-name system
Sorry I couldn't think of a different example off the top of my head. The bird site employs a dual name system, where a user has one unique name that identifes their account, and one non-unique name which is displayed with the unique one. This can be a good thing to cheer people up after they missed the account name they wanted. I don't think it is great overall, evidenced by the fact that we had people fighting for particular unique names nonetheless.
Mastodon and server-scoped names
Mastodon and the fediverse have systems where users can be on a server of their choice, or one they host themselves, meaning you can almost always get the name you want, as long as you're willing to compromise on what server you're on. It's not perfect, since server choice does have a decent effect on your experience on the site, but it works fairly well.
Bearblog and deleting empty accounts
"Domain squatting" is the practice of having an account of a particular name with no content. A large portion of accounts are left empty, and on platforms where having an account is not required unless you contribute, it's good practice to remove empty accounts after a certain amount of time. This is very effective, but still sometimes you have a simple name which is already taken by another contributer.
~ Enter Discord ~
Discord is the perfect equalizer. The way it works is that everyone can have any name they want, and everyone has some randomly generated numbers after their name. e.g. Deijin#0660. If everyone has numbers after their name, there's nothing to fight over. Peace at last.
Non-interactive platforms like bearblog are the exception, most other busy platform types should consider using a system like this, along with a verification system 𓅪 if it's used by famous people.