Preferably it would be connected with what's going on in the game, but in my experiences all the newspapers quickly ran out of things to write about. So for now things are made up. However, if you want to post something from an RP write in a way that a reporter would catch the story second hand. I also try include IC things about NPCs such as merchants getting in new merchandise.
This is a news business so they actually have people to go out and find/verify stories not just any scrap the lands in their lap. However, there is nothing to say that they won't occasionally get hoaxed, but just keep in mind that for any news agency to survive, it must maintain at least some credibility. However, if someone wants to start a tabloid they can collect the less verified and more outlandish stories too.
Also, if you want to contribute, consider making a character that works at the bulletin to give the thread a little more flavor. It's not a requirement but it is nice, and the character can only exist on the forum if you like. Although I used to have an in game character for Namae, I don't actually have one made anymore.
Here's a scenario for how to use the bulletin for an RP
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Player 1 proposes to Player 2 in the plaza and turns it into a big event getting several other players in on the act. Player 1, or any other player present for that matter, can then come back to the ONBulletin and post a bulletin. (however, please do check if the bulletin has already been posted in the case of RPs. We don't need 5 posts of the same incident, RPs can be used to flesh out information.

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Match made in Hydlaa. Player 1 put on a real performance in the plaza running a complete routine proposing to Player 2. blah blah blah...
Player 3 comes along and reads the bulletin but doesn't know any of the players involved. But, maybe Player 3 is in a relationship with Player 4 and will now start sweating and acting more nervous around Player 4 because Player 4 may have read the same thing and will now start pressuring Player 3 to get married.
Players 5 and 6 may have also seen the bulletin and know the people involved. However, Player 5 was formerly in a relationship with Player 2 and had no idea that 2 had moved on. Now Player 5 is mad and will confront Players 1 and 2 when next seen. 6 on the other hand is just friends with the happy couple and now wants to find them to congratulate them and send wedding gifts.
(For the reason that it can affect other RPs, check OOCly with characters you name, aside from your own characters, before you involve them in a post.)Player 7 is probably the most detached of all and yet reads the bulletin and thinks "Opportunity!" Player 7 then goes and seeks the couple out and tries to sell them shady "insurance" because it can be tough for a new couple starting out and "things happen."
All the while, one post has now spawned 5 other RPs which may lead to other posts which could spawn more RPs.