Doing dark themes is a very difficult job. You have to in addition make it legible as well as compatible with RES (I don't use it, but it's the bane of all reddit CSS designers as they force their own night-mode and styling).
I feel like there is too much going on with the design, especially with the link listing. The background grid lines and how its separated causes a lot of focal points when viewing comments. In addition you are also loading a 1920 x 1050 background image, while I see its necessary for the design, the grid lines cause focal issues.
The sidebar is nice but needs a lot of padding to give it room to breath, it's very squished at the moment.
Centering the submission is nice but not too necessary, it's made to be on the left to be consistent with submissions being on the left as well.
The one advice I would give you is to be simple
, the more complex the more you have to adjust during feedback. In addition the more you have to change to accommodate RES users. Also a dark theme is very tough to build so consider changing it to a lighter theme. See below the list of subreddits I've made for some inspiration.
(My first attempt at a dark theme)