The bright background is only annoying because Phoronix.com itself is so dark. Following a comments link just to have most of your monitor switch from dark pixels to bright is what makes it so jarring to look at. Either make Phoronix.com match the forum or make the forum match Phoronix.com.
The "whole width" thing is also avoided on mainstream websites for a very good reason, and not because of some archaic mistake. Longer lines of text are actually harder and more stressful to read. The distance between the end and beginning of each line of text is longer, which makes it harder for the eye to keep its place when scanning lines and requires more effort and careful scanning to read any paragraph that actually breaks across lines. Narrower but taller blocks of text are superior in terms of readability, which is why columned text layouts are so popular; the fact that you have to scroll more is a trade-off, certainly, but one I personally find more than worth it. But then, I run two 21.5" 1080p screens on my desktop and a 17" 1080p on my laptop, so I tend to have a lot more horizontal space than most.