You'll need to comment on at least one other person's link, yes. Though this does not guarantee that someone will comment on your post. Everyone is required to give feedback, but who they give feedback to is completely up to them.

We will never require anyone to use their voting power for something, but if by using the post promotion, we expect to receive a little extra support and attention, the least we can do is provide some ourselves, right?

If there are no other posts in the topic you are sharing to, this rule can be looked over. Use of the rooms will grow over time, but for now, many of the channels are empty.