The safest path to a solution would first test if a new Windows User without any special characters solves the problem. If this is successful, the two solution paths are:
1) Keep using the new User login to play
2) Modifying your normal User account
The second option is great since you get to keep your usual user login. This can be very dangerous if not performed correctly breaking your normal user login. For more information about the process, see:
https://superuser.com/a/1346983.
Simply renaming the Username in the Control Panel dialogs WILL NOT change the Folder name in 'c:\Users<username>' and Registry data associated with it.
To quote a player who successfully performed the operations:
Created a new Windows Admin Account.
Logged in from that account.
Renamed main user's folder name and changed registry entry as mentioned in a link you have previously shared.
Logged out and logged back into main user.
Checked if everything is in order. Folder name, registry entry etc.)
Ran the launcher and the game.
Worked like a charm.
After the changes have been applied, you can delete the previously created user that was used to modify your original User account.
Be aware that this might (shouldn't) affect the OS in odd ways. If there is any strange Windows behavior, this change is most likely the cause.