They're trying to seed the subreddit. If there's no content, no one will be interested, and if there's no one subscribed there'll be no content... this technique is a common way to kick start the community.
(It might be worth posting fewer links though, otherwise any discussion that does happen will get lost quickly.)
I'm experimenting with a new rationalist subreddit on reddit.com
/r/rationalisthmus
Starting with links populated from the planet rationalist data set - to which I've added about 50 new sources in the past few weeks.