Thank you for your answer @awlogan 
It is really hard to understand what are the actual features and how they work. The lack of documentation doesn’t help with this regard (I’ve stumbled upon “learn Discourse” and searched - via Google and the built-in search engine - and still can’t figure out most of the mailing-list functionalities).
@codinghorror: correct me if I’m wrong but I’ve got the feeling that discourse wasn’t thought of as a mailing list replacement from the beginning, then the mailing-list features arrived and there has been no effort so far to gather documentation about it. I can’t find the quotes back but there are a series of them in the line of “Discourse is a web-based discussion platform”. Despite my searches, I’m still unable to assess whether Discourse is a viable mailing list replacement.
What we want to achieve is offer non tech-savvy people a way to take part to the discussions that have been taking place in our mailing lists (mailman powered) so far. Discourse seemed to be a good pick because of the great web interface, functionalities and the mobile support but these were my main questions when I started looking into Discourse, I still can’t figure out the answer :
- could Discourse work as a mailing list with a forum-like web interface ?
- or, alternatively, could Discourse work as a forum with complete mailing-list functionalities ?