If the users chooses what they are shown and the order they are shown in, then it's fine. If the platform chooses, then it's not, because they will always choose what creates the most engagement.
Not necessarily. Just fix the algorithm. Showing all submissions by time should be ok, showing all submissions by number of upvotes should be ok if the user chooses that.
I think I would be fine with a positive enumeration. Some ideas for serving content:
- purely random
- sponsored but without user tracking (like old school TV ads)
- sponsored for user selected geographical area feed
- sponsored for user current location geographical area feed
- follow "friends" or influencers
- purely timeline
- discussion boards
- timeline (IRC like)
- threaded
- user votes (not magic platform votes)
- follow keywords