As previously alluded to, posting without reloading the entire page.
Something I hadn't realized was that loading a new page aborts all existing HTTP calls (including async. ones) which…could be a problem for the user, assuming that zir post went through fine and now wants to view it: ze clicks the Home button just to find that…nothing shows up at the top of zir dash.
I checked how Tumblr handled this and it succeeds by disabling the Close button and the modal