I have to say that I saw your post on Listnerds as well. Unfortunately I seem to be getting very few e-mails (4 - 6 per day) so when I get one I jump :-). It's a great way to promote our posts I believe.
I believe that people want to engage with posts but they struggle to find the itneresting ones to do so. If now they want to get mailing credits and income from listnerds they can combine both together and comment on the posts that are presented on listnerds.
Yes, I noticed there aren't too many emails too. What membership do you have? I believe high-level memberships don't receive emails from lower level ones, unless they are solo emails.
I'm actually with a free account. Seems that there aren't that many mails available at the moment.