Look at the navigation hierarchy. There are two nav background colors, but you can barely see the difference (even on a new MBP). The search input blends into the nav background, and not in a stylistic way, it seems completely on accident.

The "Community Forum" logo type looks off brand.

The iconography illustration in the masthead was mailed in. It's just the same two icons copy pasted.

The card layout at the bottom seems very un-github as well. They are typically very good at handling large amounts of text and information, but those cards are really hard to read. They bounce around from center-aligned lists (usually a bad idea) to nested columns.

I will say the community search is nice.