There are two sets of game rules. Blizzard has to follow the ESRB ratings Those pertain to the pre-made game content that gets reviewed. It is rated Teen. PLAYER made content like chat/names is created in real time and not reviewed. It is subject to the game policies a game company puts out.
Blizzard has never allowed profanity or masked profanity in their games, regardless of ESRB rating. The profanity filter exists not to excuse people breaking the rules, to but to assist parents and others as as stopgap measure for those who break the rules.
This argument is as old as WoW. 2006… People used to complain they got suspended for using profanity in game.
Still complaining in 2007
Still complaining in 2025…
For a more modern take, it is in the Spotlight on Harassment thread
Mature Language Filter (aka The Profanity Filter)
This can be activated within your Interface Options: Main menu (ESC key by default) Click Interface > Social and check - Mature Language Filter.
Once enabled, all inappropriate words in our profanity database will be filtered and masked to appear as jumbled characters, such as ‘*##@&’.
Note: The filter does not excuse the language used. The filter serves as a temporary shield, to help parents of minors and others who do not wish to see it, to block it. Our policies prohibit the use of both clear and masked inappropriate language.