Right, people tend to bring these up on Facebook, but it's typically a scattered discussion.
Are there any Facebook Groups in particular that you know of that facilitate informed, rational discussion?
What I have in mind is the instances when I read a paper (read: dozens of papers on a refined area), the methods section leaves out 10-99% of the details, and I spend significant time and effort searching for the details if they exist at all anywhere.
I'm not concerned only with "public" engagement, but informal discussion amongst a diverse crowd of academics.
(Note: a New Zealand company in this field spammed me to get me to sign up, so that was an immediate "no" to wanting to even name them.)
FWIW, I thought there was already a lot of public discussions among academics.
But you asked about public discussions, which is a rather different topic.
Apart from that, there are talks at conferences which are open to discussion with the audience.
I suppose there's not really a need for much more than that, in the public sphere. There is plenty of private discussion amongst one's peers of course.