Clarification on linking to external sites

I started this thread on the OT lounge and it was anchored. I'm trying to understand why and the only reason I can think of is because it links to a Reddit thread. It is LSU related, educational, and of relevance to many who live and work on the gulf coast. So is any linking to reddit frowned upon? If so, what is the difference between it and linking to a news site or blog? Thanks for helping me understand.