This is my paperwhite and the issue is a bit annoying - I might 'live with it' but the thing is, when I do that, then when I decide to upgrade and sell my old one, I have to sell it with an issue, which may make it harder to sell.
Would you contact Amazon for a new one with this issue? This line is consistent - when I read in landscape mode, it goes down vertically and just messes up the letters in that area. It's about 2/3 down from the top of the screen.