On 29/04/2016, wren romano
For general discussions I think this mailing list is best. I'm cool for keeping irc as a side channel for hashing things out more interactively, but it's all to easy to miss things there so I think it's best kept as a side channel not a main one.
I like (something like) GitHub issues for tracking the exact content of proposed changes and their (direct) commentary.
As far as wiki stuff goes, to be honest I'm kinda against it. I see how it might could be helpful as a sort of staging ground prior to actual RFCs, or as an edited synopsis of email discussion; but in my experience the wiki proposals for Haskell changes tend to get very crufty and hard to follow after a few changes have been made.
I agree on all these points. I lean slightly towards Trac rather than Github myself, being a little wary of enshrining other-party-hosted SaaS in a communal effort like this, but i shan't make a fuss about it. I'm slightly against Phabricator as installing PHP to work on Haskell feels very wrong.