Shift+End and Shift+Home select current line from cursor position to the end (or beginning, respectively) of the current line, if the cell is a code cell. In markdown cell they select the whole cell, which is:
1) not intuitive
3) scary, because there is no other way I can guess about to select a part of the line from the cursor position to the line end or beginning.
Please correct it. Selecting the whole cell can be done with Shift+PgDn/PgUp, if anybody needs it.
My browser is latest Chrome on Windows 7.