So, I answered a question that the asker entirely changed the content of (after I answered; edit history), should that have been posted as a separate question? Should (can?) we do anything about it (I suppose mods can merge but not ... anti-merge? split?)? Explain that he should post it as a separate question?
In theory the asker really shouldn't do that. Some argue that the answerer is responsible for updating, but I think that's in the case of less severe question edits; completely rewriting the question isn't a good idea. I left a comment in this case asking him to post separately; you're right that mods can't split questions. When/if he does the original question can be rolled back so the answer makes sense again
Edit: It looks like he did post a separate question (albeit with less detail, for some reason), so I rolled back his original question and deleted the obsolete comments