Whenever I see a high quality comment made by a deleted account (see for example this thread where the two main participants are both deleted accounts), I'd want to look over their comment history to see if I can figure out what sequence of events alienated them and drove them away from LW, but unfortunately the site doesn't allow that. Here SamLL provided one data point, for which I think we should be thankful, but keep in mind that many more people have left and not left visible evidence of the reason.

Also, aside from the specific reasons for each person leaving, I think there is a more general problem: why do perfectly reasonable people see a need to not just leave LW, but to actively disidentify or disaffiliate with LW, either through an explicit statement (SamLL's "still less am I enthused about identifying myself as part of a community where that's so widespread"), or by deleting their account? Why are we causing them to think of LW in terms of identity in the first place, instead of, say, a place to learn about and discuss some interesting ideas?