I have sat in 2K and 4K - I found the 'K' seats perfect and very private - although I would avoid 1K due to the close proximity of the staircase and toilet area. I don't know why most people prefer 'A' seats - especially in this cabin - if the person sitting in the middle section doesn't raise their privacy screen they are looking directly in your direction. In the 'K' seats there are no seats directed towards you, in fact they are directed away from you.

Some might argue that there is more foot traffic on the 'K' side, but with a total of 9 passengers on that side, it is hardly worth noting.