By default, this version of we_universal does not limit the display width on very wide screens. If you prefer to have a limited display width (with wide borders), there is a setting that you can enable in theme/custom.css:
/* Set the maximum forum width on wide screens
* To set a maximum width that the forum will not grow beyond, uncomment the following lines
* and set a value (1200px is a typical value)
Uncomment the code block and adjust the highlighted number if desired.