Part 1: Comments have died because of a fear and scarcity culture that has developed on Steemit.
Part 2: My upvotes and the engagement on my posts is directly correlated to my comments made.on other posts. Often at a greater than 1:1 ratio.
Part 3: I upvote good comments anywhere I find them. Sometimes I upvote just because they made me laugh. Sometimes I explain why they got the upvote. Sometimes I leave it a mystery.
Part 4: Are you willing to upvote a really good comment even if they didn't upvote your post?
Numbered lists are awesome!
You touch on something that leaves me feeling a little "heavy" these days, namely the seeming growth of "scarcity culture" here. And much of it is meaningless and illogical. Even a year ago, there was far more of a cooperative and "pay it forward" sentiment here; now it seems limited to little "pockets" of people who still feel hopeful... but they are fewer and harder to find, it seems.
From the sound of things, you're focused on engagement, which is cool... and pretty much my own approach. Any rewards made are pretty much "tips."
And yes, I will upvote a post, regardless of whether they upvoted my post... value is value; either the comment has value to me, or it doesn't.