Them you are free to not install them? Why ban them outright?

I'm using https://github.com/cjpais/Handy whichseems to be doing exactly what this app does, and has a very similar background story (author couldn't type die to injury).

I see, that's a really fair point. And I can understand that banking field example. So I can see why they're guarding against it. My disagreement was less with the rule itself and whether Whisperpad's specific use case for users with mobility needs falls on the right side of it.

I would like the option to allow the behaviour selectively

Pasting doesn't seem very unsafe. Especially not when the app can't know what it's pasting into.