I'm fairly new to this site but I've noticed that on the worldbuilding forum it seems common for people to edit their questions in response to answers. In some cases, these edits substantially change the question and, in turn, change the validity of the answers.
The result for those answering is that their effort is wasted on producing an answer that's no longer an answer and they also risk losing reputation via downvotes (until they delete) because their answers are no longer valid.
Should there be policy on acceptable changes to questions? Or should we just expect to have the carpet pulled from under us every now and then?