worse than the pros - contrary to popular expectation & perception.  (I think they are right, because most fora are either anarchic (eg CL) or heavily moderated  to a particular purpose.)

Built into human nature?  I doubt it.  I suspect that what is going on is that the pros make their money from traffic volume, and have learned to manage that more or less, by balancing the heat and the light - while the amateurs are in it for their smaller purpose.