I must say it is much worse when you have very pale eyelashes. People with naturally dark lashes may be forgiven for this crime. Maybe. But pale lashed ladies? Never. Extra demerit points are awarded if you dare to heavy line the bottom eyeline only, with pale top eyelashes, that are un-mascara'd! A sin! A sin!
It is okay to line only the top lid. That is fine and very 1950s pin-up which is all the rage. Lining the bottom line alone will only make you look either like a teenager from Slappersville a or teenage goth from Whanganui.
I have no patience for people with bottom heavy eyeliner. If I see someone walking the streets sporting this look, I may take out my Nana hanky, give it a spit and start scrubbing at their eyes!
Of course there are always some people (below) who can pull it off. They usually hang out on runways.