When answers are posted within a question's initial grace period, it is possible that further edits could completely change the question (see "chameleon questions"), and render those first few answers incorrect.
Worse yet, nobody is notified that there was a change to the question, except those that are sitting on the page and notice the edit bar pop in. And of those, only those bothered enough to open it in a new window to compare the differences, will see how much was changed.
After the grace period is up, nobody will be able to consolidate why the first few answers actually answered a different question. And the answerers won't know unless someone comments or down-votes (and in the latter case, without context, they still might have trouble understanding, unless they memorized the question's initial state).
I'd like this to apply to the question, as well as answers. Sometimes I (or others) have added perfectly good answers, but then the question has been changed within the grace period, making answers look foolish without any indication of what's happened.
So this time, my proposal is quite simple:
Once an answer is posted to a question within the initial grace period, a new grace period should start, and the current state of the question should be saved as the first revision. Further edits within the next 5 minutes will be aggregated into a new, second revision.
This will only noticeably affect questions where answers are posted within the grace period and the author of the question makes edits within 5 minutes of the first answer. (Effectively, it would treat it as if a different user made an edit within the author's grace period.) All other scenarios will continue to behave as they do today.
This feature request comes close:
However, the answer suggests a simple change to the wording or a pencil icon (like we see with edited comments), without adding a revision that can be viewed and compared. I don't think this is enough - in some cases it's going to be important to know what changed, not just when.