Question: Consider this situation. I post a legitimate and correct answer to a question and receive a few upvotes. Then the OP realizes that's not what they wanted to ask, and significantly rewrites the question, rendering my answer irrelevant and useless. Ideally the OP would comment on every answer saying "check my edit" but *some people don't know to do that*.

This leaves two possibly bad situations:

1. I never know, the answer stays, and the votes don't reflect the usefulness of the answer anymore.
2. All of a sudden I get an influx of downvotes because my answer isn't helpful anymore. *If I'm checking and notice my rep has dropped*, I come back after the fact, edit the answer, and bring it back to the original quality. This is great, but 9 times out of 10, the downvoters never come back and notice the answer has been edited. It might get more upvotes, but it still doesn't reflect the true value of the answer.

If we can get notified when the OP gets edited, we can nip it in the bud and go back to edit our answers to match - thus maintaining the quality of the answers on SO.

Answer: 
This is a good suggestion. I've been downvoted before simply because the question was edited changing the validity of my answer. Most people tend to realize this is whats happened but some don't. It would be good if there were such a notification so you could modify or delete your answer, as appropriate.
We are not going to implement automatic notifications on edits after you post an answer. If you would like to opt-in to notifications for this, please use the [follow post](https://meta.stackexchange.com/q/345661/51) feature.