I worry that this is a case of finding a 'secret virtue' in one's vices: I think we're often tempted to pick some outstandingly bad feature of ourselves or an organization we belong to and explain it as the necessary consequence of a necessary and good feature.

My reason for thinking that this is going on here is that another explanation seems much more plausible. For one thing, you'd think the effect of seeing someone heavily update would depend on knowing them before and after. But how many people who think of LW this way think so because they knew someone before and after they became swayed by LW's ideas?

With Nancy, I think that the PR problem LW has isn't the impression people have that LWers converts of a certain kind. Rather, I think what negative impression there is is the result of an extremely fixable problem of presentation: some of the most prominent and popular ways of expressing core LW ideas come in the form of 1) 'litanies', or pseudo-asian mysticism. These are good ideas being given a completely unnecessary and, for many, off-putting gilding. No one here takes the religious overtone seriously, but outsiders don't know that. 2) they come in the form of explicit expressions of contempt for outsiders, such as 'raising the sanity waterline', etc.