to me it looks like a bug, but it may be just an annoyance. when i select a region, and i want to extend the selection further right, i use the shift+right, but instead of getting what i wanted, it just remove the selection from the left side of the region.

you can try it, by selecting a word in any file (ctrl+d or double clik), if you then try shift+right you will see what i am talking about. btw, shift+left is ok.

another similar behavior is when using ctrl+l to select a line and then moving down with shift+down.

This is the usual behaviour for text editors on windows: selection regions have an active end, and using shift+arrow key adjusts the active end, not the leftmost or rightmost end depending on the arrow key you press.

That being said, there is still a niggle with selection regions created by the mouse in Sublime: they’re always ordered left-to-right, rather than ordered in the direction they were selected.