Players with usernames that include certain special characters cannot be targeted with commands unless using quotation marks.
The autofilling command feature does not include quotation marks around the player's name.

Players hoping to use the 'autofilling commands' button for a command relating to a player, (just /tp) will have to manually edit the command to include quotation marks around any player that has special characters in their name. This nullifies the purpose of having an option to automatically input the command.

As far as I am aware, all that has to be done is for somebody on the bug team to add quotation marks around the variable for the player's name.