It seems that Qing Liu decided to leave MSE. Know anyone why he did this? (He was QiL, QiL'8, and lately user18119. )
Some of the the reasons appear to be public, and there is no reason to believe anything about the user wanting privacy or not. He happens to have not stated the reasons, but people requesting deletion rarely have any reason to open a meta thread explaining things. The only case that comes to mind is one user who staged a public protest (it was phony but successful; he opened a new account). I do not remember anybody saying goodbye except in user profiles that did not belong to deleted accounts.
At the time of the previous meta thread about this deletion, it was still possible to check the user's recent comment history. A few days before the deletion he had tried to remove an answer after commenting that it was no longer relevant to the question. This was denied for some SE reason, and after surprise was expressed about this (along the lines, "what? you mean it is not my answer to delete?") a moderator commented with an explanation of Creative Commons licenses and such. The deletion request came soon after that.