I’m talking about GNU here.
I just can’t seem to figure out on how to use either of them to communicate. IRCs don’t save older messages, but instead logs them. And I guess for the same reason, it is impossible to discuss anything in depth.
Mailing list is really hard to read, as it is nowhere similar to forum or tree-style comments. I can’t figure out what mailing list to message to.
It’s a problem if a projects wiki doesn’t have complete information, but I’d say that’s true whether it’s about their mailing list or something else.
My text was a simple quote from GNUs mailing lists page, so they definitely have it documented.
I’m not a user of mailing lists, but I can see the use of having all correspondence neatly delivered to your inbox where it can be subjected to whatever mail client rules you want. Especially if you are active in dozens of lists.