What makes a well-supported rules forum?

Like many gamers these days, I am a member of several forums supporting particular rules sets or authors. My three current favourites are Honour Games, el Kraken and Polkovnik, covering Longstreet/Blucher/Maurice/Lasalle (and other rules I don't play), Tercios and Sword and Spear respectively. I visit them all every few days. In recent weeks it has struck me that each author has a particular approach to their public. Sam Mustafa of Honour is a regular contributor to his own forums and consults members on certain of his ideas, such as which army card set to release next. He also refers rules questions to the relevant page. He doesn't discourage players from adopting house rules but neither does he seem that interested in discussing rules amendments. His games are playtested extensively before release but once published, his rules are basically done.
The el Kraken forum is quite new so it may pick up, but despite being hosted by the publishers of Tercios, the rules' authors just don't seem to engage with forum members. The result is that newcomers to these excellent rules are left to fend for themselves, checking with each other how they interpret the system. This is a real shame as I can already see house rules springing up all over the place.
The third site is the charm. The author of Sword and Spear, Mark Lewis, is not only a frequent contributor to his own forum, but he positively encourages debate and has amended the rules following extensive discussion with forum members. He doesn't plan to make a habit of this but he has decided to keep army lists a living downloadable resource, to which individuals make contributions with suggestions for new armies. The Sword and Spear community seems to be the most active and engaged of the three, largely, I am sure, because of Mark's engagement with forum members. I wonder how these differing approaches are reflected in sales revenue....