In Users tab, "User Name" and "Group" columns have their content shortened automatically if the text exceeds 40 characters. However, Users table uses resizable columns, which removes the need for column content shortening for all of its columns.
*** Bug 889221 has been marked as a duplicate of this bug. ***
Besides Users main tab, column text shortening is applied also in Networks main tab (Description column). Networks main tab doesn't use column resizing, maybe it should, to comply with standard convention of supporting resizable column for all main tabs.