It turns out the username in question was misquoted.
So this probably isn’t a bug, sorry. I was working with bad information.
@Richardus.Raymaker as far as I know, all users that had spaces in their names had them converted to either a dot or an underscore. I dont think there are any existing users with spaces, but I am thinking about when they first sign up and put in a space. What does the system do?
Does it reject the name and force the user to create a name with no space, in which case, all good. Or does it replace the space with an underscore and let the user think he has a space in his name?
This user doesn’t have a space in his name, so it may be that spaces are already disallowed by the system, in which case This is not a bug, sorry for the confusion.
But there is something wrong with this users’ username, I need to do more testing to narrow it down.