To give more context, last week, the team behind TurboHUD released a version of this overlay tool/mod for Diablo 4. TurboHUD helps keeping track of your progression, your performance, and allows you to add quality-of-life improvements to the user interface. This mod was also available for Diablo 3, and a lot of gamers were using it.
A UX and progress tracker is getting people banned. How fragile is Blizzard? They're probably afraid this will somehow give people an unfair advantage for those leaderboards that won't exist for at least 6 more months.
I assume its less about what the mods do and how the mods are doing it. It's an always online game (whether you think this is a bad thing is a separate issue) and there is a PvP component, which means things are going to be more locked down from a mod/cheat perspective.
The article itself says the same thing.
In a way, this does not really surprise us. After all, we’ve been constantly saying that you should be using mods only when playing a game in offline mode. And, since Diablo 4 does not have an offline mode, PC gamers should avoid using even simple mods like TurboHUD.
I don't have any strong opinions one way or the other but it seems really odd for them to have this stance when WOW also has all of those things and modding is encouraged within the guidelines.
Presumably they have experience in handling stuff like this and it shouldn't come as a surprise since a lot of their other games also have modding scenes.
The sanctioned mods in WoW are the ones using the APIs explicitly provided by the dev team to be used by mod developers. If you try to create mods that work outside those APIs you are running the risk of being banned just as you would in Diablo.
To be "fair", given that for better or worse it's an Always Online game, it's easier to just say "NO MODS ALLOWED, END OF STORY" than to deal with the hassle of strictly defining what is and isn't kosher and dealing with the inevitable rules lawyering from people trying to argue how THEIR MOD is special and doesn't break the rules.