Sorry, you can't actually set your display name to anything else. It needs to stay as the name of your account, otherwise you will be unable to comment on things. It's a very old glitch with the site that likely will not be fixed.
You could name a new picto, though, and name it to what you would like as your community username. Then you'll have two pictos to work with, and use the one for your account here on the community.
Sorry, you can't actually set
Aw, Okay, thanks
Yeah, sorry about that. I
You could name a new picto,