I dont see how inflating it with Commerce posts helps matters. Does some minimum quota of activity need to maintained for the sake of appearance?
Forums require regular maintenance, and take resources away from other projects.
They must justify themselves.
crow singlehandedly revitalized this place by not playing to the crowd-norm.
So it is with commerce. You now have a functional metal forum, with news and discussion amidst the advertising.
The solution, as always, is to post more interesting stuff.
Users need to do this.
If there aren't enough users to do that... then: time to die, for the forum.
Ideas have consequences. Events have effects. Actions have purposes.