With Halo Waypoint’s new update, the custom CSS someone made for a Waypoint dark theme seems like it needs to be updated.
(Here’s the link to the extension in Chrome: Stylish - Custom themes for any website - Chrome Web Store . In the Stylish extension, search for “waypoint” to find the dark theme)
Does anyone know if an update is on the way?
You would need to poke davidjcobb about that as I believe he made it 
I’m not sure what problems you’re experiencing, but the only changes I know of are to the reply form, so I looked into that. I’ve released a minor update to make the rich text editor look better; however, I can’t do anything about the Source View (BBCode) editor due to technical limitations. 
You can get the minor update here.
Stckrboy is right, though: this style isn’t officially produced or maintained by 343 Industries. If it has issues, PMing me is better than posting here.