it has occured to me that there are questions, for which some edits change their meaning. Changed so much, that an answer is rendered irrelevant or out of scope, even sometimes attracting downvotes. How is this properly handled? How is a user permitted to alter his/her question so much?
A question should never be altered at the point that any given answer is anymore valid.
If the OP notices the question didn't come out like he meant, he should ask another question. Changes that make answers invalid should be rolled back.