I have bumped into that video, too. YouTube assumes I am interested in First Gen Civics now. Haha. I just watched it through and makpde stills... no hints of a latch. I'm out of time this morning before work, but I also googled and failed to find hints about that rear seat latch that way. If/when you figure it out, post a set of pics or a short video. Nobody online appears to know, lol.
QUICK EDIT: In this still you can see what look like round brackets for pins as a kind of hinge for the seat to fold.
QUICK EDIT TO QUICK EDIT:
So, the accord idea was bad. Deleted. This is better, from a parts site. #9 is the "locking rod" and number 14 and 15 are locking plates on the left and right below the top of the backrest on the sides, it seems: