The behavior described may appear puzzling, but in > \Z'\l'4i''four inch
the \Z'...' does mean "zero width" (really!), so the total width of this line is only the width of the text "four inch" (which is less than 4 in.). > Line 32 exceeds width. > Line 33 exceeds width. This is triggered by the two text lines Any line exceeding 4i will be reported. The .em (enddi) prevents groff from complaining about the final diversion being incomplete. all others are less than 4 in. wide.
