You always bring up thought-provoking subjects. :)
As per Twitter, I can tell you that the reason tweets may be spread throughout the day, is because only a small part of your audience is online at any one time.
Example: if @theycallmedan sends out a newsworthy tweet, and it doesn't show up on my timeline when I'm logged in, I won't see it.
I rarely search for people on Twitter unless I have a question, so posting more than once is the best way to extend your reach.
Repurposing posts might work better when referencing an older article to make points on a current one.
The other way is a "Best Of" series, which I would do once or twice a year on Steemit to share informative posts with new people. Such as the one about The Station fire which nobody saw for 18 hours when I first published it.
Yep, I get this, but it annoyed me so much a few years ago with everyone believing they had some large audience that I stopped using Twitter. For the big accounts sure, but if you have 43 followers - no thanks.
I do this often anyway, so Showcase Sunday was something different for me :)
It is good to talk about these things openly though, and at least have a chance to work out some pattern of behavior. The problem is that there is a lot of conflicting opinions, much of it with significant stake :)