I think that in case of an actual mistake, the sooner there is a self-delete, the better. Would it be possible to have an official button for accusing somebody of trolling? Suppose that two or three people clicked the button instead of posting replies. After all, an actual troll doesn't want to merely elicit a few button clicks. Two or three people clicking the "I suspect that this post is a trolling attempt" button could cause the author of the post to see that it has been identified as such, and the author could have an opportunity to self-delete the post. There would be no time limitation. Obviously, sooner is better than later. However, a little late is better than much later.