Just a few more suggestions that are completely subjective.
I'm not sure what CSS changes can be made that would affect only this forum, but I think we could do with some more white space. The new upvote/downvote icons are quite wide (in comparison to other stacks' icons), and for some reason, the entire area around the posts feels tight. The following CSS changes give a bit more breathing room:
With regards to the icons, can we not have the color entirely overlay them? The blending between the overlay color and the arrow color causes it to feel muted and inconsistent with the other non-active icon.
Also, can we have the text from the logo be vertically aligned as middle rather than baseline with respect to the buttons to its right? The baseline alignment makes it so that the logo is placed higher up, and the uneven vertical spacing of the logo slightly bugs me.