This style is unfriendly to eyes over 50 years old and to anyone with visual impairment. (I am outing my aging eyes here.) It turns reading into a chore rather than a pleasure. You can manually adjust the browser settings to partially compensate, but the best settings vary from site to site and page to page.
Besides making a general protest of the prevailing web style, I’d like to plug my browser add-on, Legibility. It automatically make these forums and other sites easily readable. Works in Chrome and Firefox, and is free.