I'm not so sure. I've been watching this since I found out about it a few days ago and it seems like it goes both ways.
I took a few people who were numbers 15 or 16 on my list (didn't automatically show up on chat list) and went out of my way to like a few of their photos. They all started showing up on chat even when they weren't online.
Yep, spot on. I had no -1s, then I blocked someone and they showed up.
Interestingly enough, under advanced options, you can also set it so ONLY certain people show up. I keep a list of girls I'm hitting on and sometimes only select them to chat with. Imagine my confusion when these were the only profiles listed under PrivacyData ;)
I took a few people who were numbers 15 or 16 on my list (didn't automatically show up on chat list) and went out of my way to like a few of their photos. They all started showing up on chat even when they weren't online.