The NYC Transit's Rules of Subway/Bus Conduct note that it is a violation to:
Place one's foot on the seat of a subway, bus, or platform bench; occupy more than one seat or place bags on an empty seat when doing so would interfere with transit operations or the comfort of other customers.
And while mansitting is indeed behavior that interferes with the comfort of other customers, sometimes it comes so naturally to subway riders that others are driven to create logos like this. Next, we hope for the "No Jerks Who Don't Give Up Their Seats to the Elderly, Disabled, Pregnant or People with Kids" logo, but that might take a little while longer.
And there's the "Close Your Damn Legs on the Subway So I Can Sit Down Already!!! Group" on Facebook. Motto: Your junk isn't that large. Close 'em up!
"No Man-Sitting" logo designer Catherine Weaver sent us a revised logo--this one "looks more like the ones on the train". Thanks, Catherine (and David Kaplan!).
And the implicit warning is that riders are onto you, man-sitters!