type some text followed by some whitespace (spaces or tabs)
put the cursor in the whitespace
press Shift-End
Instead of selecting whitespace between the cursor and the end of the line (to the right of the cursor), whitespace is selected between the cursor and the end of the text (to the left of the cursor).
Shift-Home and Shift-End will initially go to the first/last non-whitespace character on the line. Pressing it again will go to the absolute first/last position.
That seems odd to me, since Home and End (without Shift) do not behave that way.
I'd like to suggest:
* Make Shift-Home/End work like Home/End
* Add a preference option for enabling/disabling the functionality you described for Shift/NonShift-Home/End.