There might be data mining in current add-on (Stylish). SimilarWeb( A datamining company). You can opt out, but am not sure how effective this is. Complains have been made. Not sure what will come of that. If you need the features then it must be accepted this can happen. There are forks as mentioned by Matt in posts below, but they too are unknown at his point. I need and want the new stylish feature, but not the bad stuff.
Edit: 3rd Sept (2016) Added some extra URLS to the Opera/Chrome section below, and also updated both Opera/Chrome and Firefox CSS files and links to v004b.
Some small updates to my stylish add-on CSS. (v004b) Its been working well for me on Opera (latest).
Save your eyes from bright screens with the dark forum theme.
Also this time better links and info below for Opera/Chrome (which I use), and Mozilla Firefox version of the Stylish add-on CSS.
Opera / Chrome Stylish add-on CSS - link (v004b)
Click to create a new Stylish entry and copy and paste the CSS from the link above into the page and name it and then save.
Then in the stylish add-on manage page for this new style (opera/chrome).
Add these below using the option 'urls starting with':
Maybe for you using the * wild card will work at the end of just a couple of URls... for me it didn't for some reason and some forum pages like badges, bio profile etc would revert to forum default white. So I added these urls above.
The FF stylish add-on CSS below already has these URL's included in the CSS. And you create it the same way by adding a new styilish entry.
Mozilla Firefox Stylish add-on CSS - link (v004b)
Open on windows with wordpad to edit outside of stylish - or your preferred CSS editor. Let me know if the links don't work. Scanned CSS files with anti-virus program before uploading them. If you right click and 'save as', please scan them yourself before use. Otherwise just open the link in a tab and copy the CSS direct into a new Stylish Add-on style page for both Opera/Chrome or FF.
It would be really good if we could have an installed Discouse dark and or semi-dark theme to choose from at some point in the future. Not to detract dev time from game development though, as and when @INovaeKeith