Consider this thread, in which the user asked a question, received an answer, and then asked others to delete the question after receiving help. I have never seen this before, and I am not sure what the proper behavior is in this situation. Note that this is different from historical questions on meta such as this situation in which users would simply delete the question. I have never deleted a question I have asked, and am not knowledgeable of exactly which privileges are earned when, but I suppose it is possible this user is simply unable to delete their question, but either way it would still be problematic, as the previous discussion has shown. Note that in the second linked thread, Asaf proposes as a counter-measure to vote early and often for answers. In this case, this solution won't work, as the question has not been deleted but just vandalized.
So what should I do in this situation? Is it possible to 'roll back' a thread? I feel like it is counter to this site's purpose to vandalize one's question in this way, probably to avoid being incriminated for cheating in some sense.