What keeps HN relevant and high-quality is the flagging and voting system, and I don't know how that translates to a git-based architecture.
EDIT: I misunderstood how github's pull requests work. Sounds like a perfect tool to maintain community standards.
The community would vet articles and potentially help with editing and clarity. This would help contributors make sure their articles are well-written and well thought-out, while giving readers consistently high-quality content.
Of course, this requires an at least moderately engaged community of contributors, but I think that's completely reasonable. We would also have to be careful not to scare away insightful people who aren't great writers, but I think it would be manageable.
If it is not associated to HN, then this is not an easily solved problem.
Basically, we should just have a community where the person managing the github account and whatnot is more like a sysadmin than a CEO. The main goal should be to find somebody willing to do a little extra work to get everything working.
Perhaps, at the very beginning, the submitter could just take care of all the administration (hopefully it's not too much work) and everybody could work out a system for discussing and approving posts as a group.