Inspired by this question here.
I recently updated my twitter app and as I was scrolling up through my feed, I wanted to post something. After about 30 straight seconds of scanning the top of the screen for some way to post a tweet, I found that this feature had been moved to the bottom of the screen.
From the previously referenced post, this breaks the generally accepted logic there. Chat windows have their input on the bottom because we read them top down. Twitter, however, reads bottom up. From this logic, wouldn't it make more sense for the input to be at the top?