Quote Originally Posted by Menriq View Post
Just to play devil's advocate, the largest MMO by far allows third-party tools (addons). Not sure this point really stands.
There's a huge difference between using addons that hook into a framework added and supported by a game's developers, and unofficial third party tools that work through memory injection. With a supported addon framework developers can pick and choose what players are and are not allowed to modify within the game's client, where as unsupported third party tools basically have no such limit and can allow players do to things that entirely trivialize or outright automate gameplay.

Blizzard has in the past, on multiple occasions over the years, actually reigned in the amount of functionality supported by their addon framework because creative individuals were able to make addons that circumvented too much of regular gameplay.