So......was this an April's Fools or not? >.>

Wouldn't this create an echo chamber where users keep noticing more from what they personally agree with, and consequentially less from the rest?

Facebook caters to you, the user. Less Wrong, in my opinion, should revolve around the topic of discussion, not the users participating in it and what they value as individuals.

I think it wouldn't be harmful if activities from users you routinely upvote are made more visible to you in your "main page," "feed" or whatever it's called here. But once you enter an article and an open discussion is set in place, hierarchies should dissolve, not be accentuated. After all, what matters to us beyond a user's personal profile is the quality of their ideas, not who they are.