Hi Peter, I have been reluctant to reply here, for two reasons. First, being a literal type, I know little of the the history of Moodle forum and have little interest, and second, I do not work in higher education. Essentially this means I work with kids who's idea of critical examination and discussion starts and ends with "That sucks!" I keep telling them that is is OK to say something sucks, but they have to back their statements up with evidence. I will get glimmers of such provision, but usually, evidence stops at "Because it does."
Forums are for adult learners, great in unis and training colleges, not so good for middle or high schools. They can be for younger students, but whenever I have tried it, it has always been shutdown with varying degrees of acrimony. Perhaps I should stop doing this in the industrial rust-belt schools I have been working in and try for a leafy green school - but that would not be anywhere near as much fun.
Forums have a place, but realistically, that does not need to be a Moodle Forum, WordPress, or Elgg may be just as useful for conversation, but then so is in-class discussion.