So that's the one blocker? Creating an issue via email?

No, the blocker is setting up mailing lists with a forum-like interface (cf. discourse), but integrated to github (uses the github account) and without actually having to do the setup. Also, without polluting issues.

Actually opening issues via email would be nice to. Trac isn't perfect, but I remember email2trac[1] quite fondly. Combined with email notifications on change, it made it easy to forward bug/error-reports to a trac instance, and automatically create an issue. Or just let support@ go straight to trac.

I still think having an email interface (as in: in addition to a REST API) is very useful. Having a web interface as well isn't bad either.

[1] https://oss.trac.surfsara.nl/email2trac

Good project-specific labels to GH issues solves the "polluting" problem. The label/tag system is nicely flexible.

It sounds like what you really want is nested threads and top quoting and/or interstitial quote/response features?

(Arguably what you really need is commonly called a conference.)

You can do that via API, so it's pretty trivial to set up using an integrator like Zapier or tray.io.

Too bad you can't open a pull request to GitHub.com, no?