This question had a conclusion that I added after testing all of the submitted answers and updating to a newer compiler. This conclusion had information that can't be found in the actual answers. The edit was done by a diamond moderator, so I can only assume there was a good reason for the edit, but what is it? I'd really prefer my text to be left alone.
First of all, I apologize for not mentioning the reason behind that edit in the edit summary or as a comment. I do make similar ones quite often on this site, but sometimes I neglect to mention the reason.
As it has already been stated by others, the edit was done to remove what appeared to be an append of improved code, among other things. I probably would've removed it when I made the previous edit, but I must've missed it then. Although it's true that the question's time was before that of the new policy, you can still post it as a self-answer for others to see. And as it was mainly taken from another answer, it should also be CW. More info on all of that has already been linked in @rolfl's answer.
Taking a couple of guesses here, but your question has just been awarded the Famous Question Badge. I would imagine that Jamal saw that badge go through, and then looked at the question, and figured it needed to be a better example of site policies.
In general, I would not advocate retroactively and 'blindly' applying policy changes to 'older' questions. In this case, given that your question is very highly viewed, it should be a good example of what we want Code Review questions to look like.
The reason that we don't like changes to the question is because it adds confusion to the answers... should new answers critique your 'conclusion' code, or the pre-answer code.
My preference is for high-profile questions to be good examples of best-practice for the site. You asked for a reason for the edit, and you also suggested that your preference would be to leave the text alone....
As has been suggested in a comment, the logic behind the policy is laid out here: For an iterative review, is it okay to edit my own question to include revised code?
Leave the question alone
A self-answer would be a good option at this point (even this late in the day). If you don't want to do that, I would be happy to roll-back the edit, and add a note to the question with a "Please note, this practice of self-answering as an edit to the question is no longer allowed on Code Review, please see ..."
Your call, preferences?