Another concern I want to make sure is represented, is that including pinned posts in the "new" feed would horribly break many bots that follow the new feed for recent posts, are not coded to expect pinned posts there, and would greatly increase the amount of data retrieved if every single query suddenly included several kb of announcements that aren't ever needed by the bot. If this is implemented, please make sure there is a way for API clients to exclude pinned posts, perhaps a new URL parameter, e.g., show_sticky=false or something. While I see this as mainly being necessary for the API, this parameter could also be used by communities to link to feeds that don't including pinned posts in them, if doing so is desired by them.

For backwards-compatibility, Reddit might want to make this the default when accessing the API, or at the very least announce this parameter in advance of making the change so bot operators/wrapper developers have time to set this to avoid interruptions. It would also be possible to just always exclude pinned posts from the API, but doing so would make the user experience inconsistent for clients that are not bots, such as 3rd-party clients (though it's not like those have been permitted to have any semblance of feature parity for ages anyways). Making it a parameter is clearly the better solution.

As for the other questions, 1, it would be useful for communities that have links to the new feed to be able to have pinned posts there still seen by users, and I'd even go as far as to say that it'd be nice to have a default-sort option for post feeds; R4R communities in particular see a ton of bias in what gets upvoted, so default-new might make sense for some of those. 2, the only concern I'd have for this is with the API as noted above.