In this answer, mod Yannis says:
invalidating existing good answers with a radical edit to the question is not... good.
The accepted answer on that question, as edited by Yannis, says:
If the edit makes the answer invalid/meaningless/incorrect, whereas it WAS valid/meaningful/correct for the old poor question, then such edit should not be made. I am unsure if it's against the official SE rules, but I agree with your concern that it is at best, poor etiquette towards the answerer.
And Yannis says here:
editing becomes less of an option when there are answers, as your edit might invalidate them.
Yet all of these meta posts are about making edits to someone else's question. Is this guidance meant to apply when OP edits his/her own question, because what they asked is not what they intended?
Editing one's own question to invalidate an existing answer can be defended with "My intent must not have been super clear, so I've clarified. That's what the edit button is for." (This is when the question as asked was reasonable, even if it might have fit better elsewhere like Law.SE.)
Are edits to one's own question, that invalidate one or more existing answers but change the question to be more like OP's intended question, encouraged, discouraged, or something else?
I give the repeated name so as to not be accused of presenting multiple quotes in a way that makes it seem like they're from a broader diversity of community perspectives than is accurate.