Maybe... "Watched the latest episode of Reign? Discuss it with us here on the Reign Board on Fanforum." or "We know you have LOTS of opinions about Reign's latest episode. Share them all here on the Reign Board on FanForum." Something like that, only
not lame.
Then just provide a link to the episode discussion thread.
I don't know if it will really work, but it's worth a shot. Do you think it would be helpful for the Reign Board to have Insta account? There seems to be a lot of Reign fans on IG. I know I've tried to promote rewatches, trivia and survivors on twitter and tumblr, and it didn't seem to be that effective.