@Schneems @avdi I'd just leave pull requests at https://github.com/mastodon/mastodon/pulls and wait :) As far as I see, the core developers give reasonable decisions as to which of PRs they'd merge.
For design principles, it'd be worthwhile reading through https://blog.joinmastodon.org/2018/07/cage-the-mastodon/ (once the origin sever comes back :mastodon_oops: