I think that sometimes a bit of "perspective" helps - I've moderated, and been chief admin on other forums for some years - one of the biggest bugbears of any forum is "spam" in it's many forms - often of the crude "todger pills" variety, but nowadays the means to spam are getting ever-more sophisticated - there are even "automated comment spammers" that will make seemingly innocent posts on a forum under a couple of pseudonyms, all just to drop in a link for a product or service.
So, what it boils down to is that "admin" probably spends a great deal of time and effort keeping the forum spam-free, and a nice place to be, and is sensibly applying a "no spam" rule (without which it is almost impossible to decide where you "draw the line"), and as an adjunct, on forums it's generally accepted that to just post any link that could possibly be construed as commercial is looked upon as being "bad form" (at the very least, consent should always be sought first......)