I did some time ago offer the DSM (Diagnositic and Statistical Manual)
as the authoritive reference we shrinks use for characterizing mental
illness.

Often pathological labels are applied if a subject exhibits perhaps 5
of 8 different traits. Mr Mx presents as having more than enough to
earn several labels -- but troll is not (yet) considered a
pathological condition.

It's not nice to use technical language in a lay group, but some
things do not translate into plain English well so you'll have to put
up with it. "Loser" and "Nutty as a fruit cake" are the
characterizatrions I'd use. You can ask your personal psychologists to
translate them.

I know it's common here to question professional reference books, but
we need to use the DSM to get paid -- that's good enough for most of
us.