From memory, the easiest way to have the "top" of a table view at the bottom of the screen (like in Messages, so the latest message bubble appears at the bottom) is to flip the table view upside down using an affineTransform and then also flip each cell in the table view upside down as well (so the cell is the right way up again).

This means you can insert new rows (message bubbles) at index 0 and they'll appear at the bottom, which makes it considerably easiest to add new messages.

This is usually because the default scroll position of a conversation is at the bottom rather than the top so it significantly simplifies scrolling logic (which can get pretty complex).

I am surprised they are using a table view rather than a collection view for this though.