i can personally tell you that does not happen. there are 'not subtle' attempts to 'stroke' advertisers to a degree, but never seen any advertising related moderator actions. i personally posted plenty of VAC criticisms over the last 2 years since i had the VAC Statement 450's in my room for 3 months.
and the cables that Von Schweikert sells, Masterbuilt, have taken lots of serious flack on WBF over the years. the speakers, which i used to own (VR9SE in 2004-2005), are not (or very rarely) criticized only because they are very good.
you can make a case that the footers that Steve Williams sells get plenty of promo, but certainly no more than happens here. and Steve gets a bit of flack (some from me) for that on WBF, but it's never moderated.
every product on WBF is fair game. 'troll-like' fly by comments get deep sixed.....but that is rare.....and 'form' not 'product' related. i've seen intense criticism of products of advertisers not get moderated when i thought it should be. and the site owners are not dictators at all, there is a good level of back channel communication when there is conflict.
plenty of politics and intrigue on WBF of course, as there are on any intense hobbyist forum. justice is not as blind as it might be.