Subtle changes, bugs and feedback

I suppose it's too complex to have an username and how we'd like it to be displayed?

It makes little sense to have both.

How you'd be displayed is how people would refer to you, if you're then asking them to refer to you as someone else... then surely that should be how it's displayed?

It just creates a major UX issue, and yes you could argue that emoji usernames do too... but when the obvious upside is that people can use their native language in their username (i.e. if you happened to be a Hungarian mathematician and wanted to use your real name you could actually call yourself Erdős_Pál without fear that the system would crunch your name... though unfortunately you'd also be dead and would not care about such a system).