As a Mac application, the option + arrow keys should move me around the file. You have support for left/right, but are missing up and down.
The Apple Human Interface Guidelines say that Option-Shift-Up should
Extend selection to the beginning of the current paragraph, then to the beginning of the next paragraph.
And likewise for Option-Shift-Down:
Extend selection to the end of the current paragraph, then to the end of the next paragraph (include the paragraph terminator, such as Return, in cut, copy, and paste operations).
This doesn’t work. Also, the same key combinations without the Shift key should simply move the cursor to those locations.