It seems to be lowercase m, actually (I copied that from their forums), and pressing it twice opens the account details. Not the most useful one, I agree. I'll probably use ",", "." and "/" though, I'm usually avoiding to use the mouse for simple things if I can.This doesn't do anything for me? The rest are interesting, though it's debatable whether really useful.
You're right, I've seen Shift+Enter (or Alt+Enter) for line break in other editors when Enter meant something else, like Excel. I welcome the extra functionality, and splitting quotes with Enter is very useful, I used to copy the quote BB code all the time in the "old Watch".