Demonstration of the FWHM-compatibility procedure. In the left panel, we show the original sample of 252 filament (purple) and 162 non-filament (green) galaxies comprising the full set of 414 galaxies. After removing 95 filament and 29 non-filament galaxies, we are left with the distributions on the right, whose FWHM distributions follow each other very closely. In both panels, the median FWHM of each population is shown as a dotted line. The medians are identical after the procedure.