The Reddit-style presentation of topics and ranking comments isn’t really conducive to lengthy, quality discussions that persist over a period of time.
I don’t know whether @Penguincoder had all these in mind, but as far as lengthy & quality discussions go, everything you wrote to support this sentece, in my experience, seems 100% correct. There was a time, when forums when used more, during which a discussion on a subject would carry on for weeks, even months, between different individuals. Taking the time, thinking over the subject and coming back with a response after days was not at all uncommon.