What is better, to erase/hide mistakes from the past, or leave them and learn from them?
The question was asked years ago, when the MathOverflow forum was hardly a year old, and the community was still working out what made an acceptable balance of professional and popular questions. That the question you mention is still around is because it got some answers which were voted up, and one got accepted. The system does not automatically delete such questions, nor do the moderators. That it got such a badge shows how to write a question with great appeal.
To answer the question of "What do you think?", I think it isn't a big deal, and that the question mentioned can serve as a useful guide. I don't see questions like that on this forum now. And the author deserves the badge technically.
Gerhard "It Isn't Really A Problem" Paseman, 2016.04.21.