To reproduce, make some lines in a text area (more than one page) and hit Shift + Page Down on the second line followed by Shift + Arrow up. I expect this to diminish my selection so I have one page selected minus the bottom-most line. Epiphany and Midori instead expands the selection by adding a line at the top. I'm not sure whether this is just a bug or intended behaviour, in the latter case, please reconsider as it is the opposite of every other text area I've ever tried. :) And it is pretty annoying, e.g. when writing Gmail, it quotes the original email in full. So I use shift+page down a couple of times to select most of the quote, then shift+up arrow to fine tune it. I have not yet discovered how to work around that.