Entities can be summoned with selector tags that cannot be selected for

The bug

Entities can be summoned with Tags entries containing spaces. However, neither the tag argument selector nor the /tag command support them.

How to reproduce

1. /summon minecraft:creeper ~ ~ ~ {Tags:["hi there"]}
   

2. Try the following

   /execute if entity @e[type=creeper,tag=hi there]
   /execute if entity @e[type=creeper,tag="hi there"]
   

   /tag @e[type=creeper] remove hi there
   /tag @e[type=creeper] remove "hi there"
   

   Note: The first /tag variant is even suggested by the command syntax help
   None of these commands is considered valid