changes the profile menu items to be displayed in multiple rows rather than a scrollable container
hides the name from the menu as it's already in the sidebar or the overview
adds some space between the menu items as a personal preference
If you don't want the username to be hidden, remove the 'h2' part. Though the other changes mean the name will be displayed in the upper right of the container instead of where it was before.
If you don't want the spacing between the menu items, remove the 'li' part.
Note that your browser needs to have support for css nesting for this to work as-is. You can see here which browsers have support and from which version onwards.