I mean...You can....but then you'll end up pulling out a duplicator when you try crouching and moving to the right.There are already third-party client mods that do it, though.
I still disagree with shift being crouch.
What else would crouch be?
You don't need 3 fingers for wasd though. And even if you really wanted to, you could just use your middle for x.
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You don't need 3 fingers for wasd though.