I like how Benedict Evans describes the 140 char limit: lossy compression.
It's hilarious to me that a rule enforced by external technical reasons (length of SMS) has become so important to the product that it's non negotiable.
Why can't I even, for example, add a text "attachment" the same way I attach photo, video, links, etc.? There's something hilarious about the CEO of Twitter screenshotting the "notes" app on his iPhone in order to send a message.