I'm glad about the work on the sidebar so far but it's still a bit lackluster. For most of the page, if one scrolls down, it's absent. Here are my suggestions.

It takes up 1/3rd of the page width.

This creates for a better reading experience by making the space for text not too broad. (So that a newspaper effect is created.) Don't worry about there not being enough space for link text. One would need a very slim monitor for 2/3rds not to provide enough width, while most people have widescreens.

Chat directly underneath the create section

and it still stretches to the bottom of the page when scrolled to the top. The added width and height will give the chat box more use without expanding it. Currently I can't even read a single message if it's more than a few words. Additionally, there's a fixed minimum height, so if the window isn't high enough, the input box will end up beneath the bottom of the scrolled-up screen. There's nothing wrong with that, people scroll down pages. (And when they do, they will see Sub of the Now, Suggested subs, and search.)

Mini-map beneath search.

This gives an overview of the comments by simply mirroring the comment tree, but only displaying usernames. Clicking any of those names will scroll the page to that comment. Additionally, new comments are likewise highlighted with a gray background. This is the real use of it: quickly discover new comments as you revisit an already seen thread. And because the sidebar is darker gray, there's added contrast compared to in the body text. (That should also be fixed, there are contrast issues on the website in general, but that's separate.) With a mini-map there's continued use for the sidebar even as one scrolls down.