Seems like a pretty readily used vulnerability. I remember back in high school on AIM someone made a username very similar to mine and said some nasty things to a girl I was talking to - she told me to stop talking to her and I didn't figure out why until years later. I imagine the same exploit could be done more easily if you can use the same username and discord actively tries to hide the hash.
Maybe I'm just overly sensitive since impersonation has hurt me, though.