story
That's because Home and End keys on the Mac, like in the original UNIX, mean the beginning and the end of the document not the beginning and end of a line which is a Windows thing (and since Windows is the overwhelming presence, is commonly misunderstood as the keys themselves meaning that) and since most early Linux desktop environment's aimed to duplicate Windows, is also the default Linux behaviour now.
You will find this behaviour in all Apple provided applications as well.
> I cannot work without a way to move the cursor to the beginning of a line
Anything that doesn't override Cocoa's default key bindings will be able to use the emacs key bindings as well (Cntrl-A for the beginning and Cntrl-E for the end of the line)
>in the new Gmail compose window, not even Command-Left/Right works
cntrl-a and cntrl-e work.