Topic on Glossary talk:Controller
In 100% of causes it's caused by "whatever thing a game is reading inputs from".
Aside of this, as I was saying here it all depends on what you consider "norm". Game being pedantic or controllers being off-center?
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Ok, I'm kidding, of course the problem is game working unexpectedly (and while you can play deadzone-aware games with digital controllers, the contrary is awful).
And having no care of deadzones is game-specific then, so absolutely it should be mentioned in each page.
And in Controller page too. For as much as probably no XInput game suffers of this issue (given testing happened with X360 controller).
Still mentioning x360ce (or Durazno, or omikron fix, or this, or whatever) is worth. And same, and even more, in the DirectInput case.