See this image of TeX Stack Exchange:
This shows the user's reputation. But Mathematics Stack Exchange doesn't show it:
This is the result of your browser's zoom function; you view the TeX site at 110% of the original size, and Mathematics at 150%. At 150% zoom, there is less space available and the responsive design switches to mode which displays less information in the top bar. When you set the zoom to a lower level, everything should be fine.
(apologies to future readers for the blue freehand circles, which were needed because the OP used red)