sure, but at the same time, you're not forced to add random gibberish. for example, you could call yourself something like "Justinzobel" instead, which is unlikely to be taken, and then use the display name "Justin"
like, yes, for very common names you're gonna have to add something to the end, but it can be anything you like! doesn't have to be random numbers, and even if they are, you can still choose them. forcing a random #0000 sequence is quite different than that. and if your username is relatively unique (like mine, for example)
you can also still make the same argument against discriminators, since paid users can choose their numbers. you might argue "many people want Justin#0001 (or any other common numbers like 1111, 2222, 1337 etc), but since that's likely to be taken, i have to use random numbers i don't like", so it makes very little difference in practice.
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Comment by @Justinzobel
Comment by sanku