I'm not sure if the happens elsewhere, but when I was in the manilla room, someone joined it and there were two of them. I'll put an image

This is a known bug:
https://itch.io/t/2450961/known-bugs-read-this-first-before-posting#:~:text=The%20player%20might%20not%20load%20correctly%20on%20rare%20occasions.%20(You%20will%20know%20when%20this%20bug%20happens%20when%20someone%20has%20two%20or%20more%20names%20on%20the%20leaderboard)

And yes, it happens elsewhere as well. I have no idea what causes it though, it would be very nice if you could find out what makes this bug happen.