There are plenty of other forums that keep similar sections hidden
Most forums that I am familiar with host Marketplace sections to enable members to sell to members - simple as that. That
is what
their Marketplace sections are for. They allow members to post individual 'For Sale' offers for other members consideration. The method of moderating this facility does vary.
I can't think of
any that allow people to advertise en masse with links to their own commercial sites - whether hidden or not

MP "Young, dumb and not here for an argument"