On the BTT forum we had members who actually worked for certain news sites and were paid for every link they posted, which of course was not allowed and in the end some of them were banned for spam. I'm not saying that's the case here, but I see only two possible options why someone uses one source in all posts - he's paid to promote that news source, or it's an account that controls that source.
I have the opinion that apart from the interaction with other users, which is obviously not there, a rule of one topic every 24 hours per user should be introduced in any press board.
I know that in BTT it is (or was) a common practice for several users, but as I said, I have never seen any post from that user where he explicitly says that he works for that website (or for any other website). Setting a daily limit could be an idea, but as I say, that user has been doing the same thing for a long time, so I think that in this case it is best to wait for the administrator to rule on this issue.
I suppose the 24 hour limitation could be useful, a suggestion in the corresponding subforum would be interesting to see if more users support the idea.