Not sure there is a common pattern. The former case had to do with certain privacy realizations, I think, and the latter case was a lack of fit between the person and the local culture.
I think you just provided me with more evidence that there are more cases than I explicitly know about, because the not-announced one I had in mind was someone whose fit with the local culture was (I think) just fine.
[EDITED to add: But clearly we have the same first case in mind.]
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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