As I said, if there is hypothetical post from 49 hours ago with 10k upvotes, you will not see it, but you will see one from 48 hours ago with 1k upvotes.
Not necessarily true. You can build an index and keep a cache of the N posts by each sorting method. Your data store will grow linearly with the number of sorting criteria you will have, which should be small.
But what about mobile?
We are talking about an amount of data that a sqlite database process in a breeze. My K-9 email client can handle all my 20 years of gmail…