I'm using 1200x1600 monitors (in portrait mode) and see a horizontal scrollbar on all of my user pages.
The user page hasn't been updated with the responsive design yet, and 1200px isn't wide enough for it with the left nav enabled.
I, too, use windows that are not humongously wide, and I disabled the left nav as soon as that option became available so I could reclaim the wasted space. (You can still access those few links on hover.) If you want to change that setting while you wait for responsive design, go to your profile -> edit profile & settings -> preferences and look for "hide left navigation".