Can't do a screen shot, but it's the horizontal line between posts, and since it is part of a grid, the vertical lones down each side of the posts. Basically the frame! Also darker shading underneath the quotes would be welcome, to make it more obvious where the quote ends and the response...
Between the posts (and down the sides as a result as it's all part of the frame) and behind the quotes - and a deeper blue for the name of the poster being quoted.
I'm OK with the size of the font, but the depth of shading - yes please! Likewise with the very pale blue text and the very, very pale blue text - black on white I'm fine with, but nearly invisible pale blue on white, not so much.