> people have the same names in real life and we've learned to deal with it.

Yes, mostly by having systems that refer to people not by their names, but either by "universal" opaque IDs like social-security numbers, or by attaching to their name a system-specific hierarchical ID like a mailing address (because you're probably the only John Smith living at your address; if you weren't, it'd probably annoy you so much that you'd likely use a nickname.)

The "usernames" that this debate is about aren't "display names" (those can indeed be arbitrary), but rather basically "URL slugs"—things that allow you to target an email to that person, or to make a web request for the right person's content. Those have to be unique, in the same way that an SSN has to be unique. (They're primary/partitioning keys.)

Usernames, as URL slugs, are meant to be a "more readable, if possible" and "shorter, if possible" version of the opaque unique identifier, where you can maybe get something memorable and vaguely-resembling your own name, but where that can't be guaranteed, because a username—as a URL slug—can't sacrifice any of the properties of a unique identifier.

That's a really messy system when you're a communications platform which revolves around the ability to @ people based on their username.

On Twitter or a forum like this for example, unique usernames are probably essential, because the alternatives are too confusing.

That could just be a UI issue. On 4chan, you just click the post you're replying to and it will automatically fill in their post ID.

Or drop the alpha chars altogether and just go numeric. It worked for CompuServe. Everyone's ID was an octal number. 72167,4531 for example.

That way there is no overlap, and nobody is slighted when they find out that their name is taken.

Compuwhat? sorry, never heard about it. (which might or not be related to this decision)

ICQ uses a number, but yeah, how many people still use it?

Yeah, I like that the arbitrary nature of non-meaningful names frees us from all these drawbacks and compromises. A simple system. But outside of strictly pseudonymous places like 4chan it erodes the concept of a unique username altogether. If you're always gonna type a display name and choose from a dropdown, why even display the numbers?

Plus, now that the identifier carries no meaning, you can't type "@realdonaldtrump ..." and expect people to know who it refers to, you'd have to type "@aae0450, Donald Trump ...".