I think this is a great word to describe the phenomenon we are talking
about. It's very easy to stereotype such people as being trolls or
deliberate troublemakers, but it's hard to reconcile that with the
amount of good work they also do.
Something which is brittle can also be beautiful and functional. Handle
with care. :-) The only problem with brittle people is that they don't
bend, they break. So the rough and tumble of social interaction on
Wikipedia can often deteriorate very quickly in a way that less brittle
people have a hard time understanding. Moral condemnation comes easily
to hand, but it isn't always appropriate, and in any event is rarely
productive.
As with many others who have answered David Gerard's original post, I
have no answers, but I think the question of how we can better serve
such people is a great one.
--Jimbo