In certain space-restricted games like La-Mulana and Hydra Castle Labyrinth, the player's Y vector is not affected when hitting a ceiling. This allows them to "hang" on the ceiling to complete the full jump arc.
A checkbox option in the platform behavior properties, similar to the double-jump, would be great.
It is a very simple modification to the plugin - in C2 I would simply delete a single line for this feature. This doesn't appear to be as simple in C3, and doing it with events is troublesome.
I've attached a .gif to give a better idea how this works.
This is available in r118 as a new "Set ceiling collision" action.