Yeah absolutely, hence why I said github-like. What I mean by that is something more modern, that supports such review style. If only Github supported mailing lists...
There's still the aspect of handing over the control to a third party that may disappear next month, discontinue the features you rely on, etc.
FWIW, I don't think the workflow is a major barrier. Do 'git format-patch' and submit it to mailing list is about as simple as it can be. It's all the other stuff (complex code-base, going through review, ...) and fairly high bar for quality that makes it challenging.
