Well, I will talk about how its different.

Posting Freebies, Promotions, giveaways is different in the sense that spreading a good news basically and it does not infringe any copyrights as its a news not a original content created by someone.

Whereas any articles like tutorials written by someone in a forum and then even posted by by same person infringes the copyright of author plus the forum. Even though technically , it looks like no problem if the poster is same guy, but if either of the forum "terms of use" or "rules" say that no content shall be copied without permission, it means problem for the other forum legally.

As forums are run on the web, it does involve legal issues and as a admin, \i am just trying to avoid issues like that.