I don't think this has been explicitly mentioned on Andrew Broad's list of quirky features, or in his Advanced JSW/MM Trainer documentation...
In JSW, Willy cannot gain access to*, by jumping**, a platform that is located in cell-row 2 of a room. This is because whenever he jumps, he is raised up by two and a half cell-rows, so either he doesn't achieve a sufficient height if he jumps from a platform in cell-row 5, or else he breaches the top of the room and moves up into the next room if he jumps from a platform in cell-row 4.
(*In order to be able to stand on it. **Of course, he can access such a platform by walking up a Ramp or climbing up a Rope, or dropping down onto it from the room above.)
This could give rise to interesting Promised Land/Forbidden Holy Ground effects. e.g. if such a platform leads to an otherwise-inaccessible sideways exit from the top corner of a room, and the room above has a solid floor (so there's no possibility of falling down onto the high-level platform).
However, it might be possible to access such a platform if the Superjump feature could be properly configured (over and above the fix which John Elliott devised to stop Willy from falling through floors once he has reached the natural end of his jump cycle, but which still allows him to fall through standonable cells during the early part of his descent from the apex of his jump).
Edited by IRF, 27 January 2017 - 03:02 PM.