Several posts for which the *Great Answer* badge was awarded were [erased](https://superuser.com/badges/25?page=2) (for lack of a better term).

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I didn't think it was possible to completely remove posts from the site. In fact, most other posts in that list are deleted and still visible to 10k+ users.

[This question](https://meta.stackexchange.com/q/86195/151367) is about revision deletion, but doesn't mention whether whole posts can be erased.

[This topic](https://meta.stackexchange.com/q/100725/151367) is the only mention of that message on MSO, and it was just a bug there.

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What's going on here? Is it a bug? Were those posts deleted deliberately? Is it possible (e.g. for the developers) to completely erase posts, and when is this done?