Xbox Live gamertag issue

When you try to join most servers on an Xbox account with a space in it it says invalid name. This needs to be fixed by Maybe replacing the spaces with underscores on sign in. I think this will be a very important bug to fix before the better together update as many people with spaces in their gamertag will be experiencing this issue. And I know thins issue isn't probably going to be marked as a duplicate but I think this is an issue that needs to be more recognised.