I've seen it with people religiously sticking to an optimal typing method which limits their hand movement to an extreme. They were crazy fast but RSI was a common subject of discussion, regardless of posture or hardware quality.

We had the same issue with gaming controllers, some with guitar learning etc. There's a limit on how much we're able to repeat the same movement again and again, it depended on what movement and who did it, but the only ones who didn't get any RSI simply avoided extreme repetitions.

And buffs. Sometimes building more and more muscles solve the issues entirely, if that's what you're into.