I mean this is true of most communities really. People dislike blatant self promotion, no matter the medium. If you're not already a valuable contributor to a community, advertising your work there will get you seen as deeply suspicious at best.

It's just that most marketers seem to be incredibly short sighted, and wrongly assume that doing nothing but marketing their own product/service is somehow the way forward.

Also any forum or subreddit dedicated to self promotion isn't really worth bothering with. Your audience won't be there, just other marketers trying to promote their own stuff.