When jumping onto random blocks at seemingly arbitrary times, you may receive fall damage (or may not, again it's completely random). I find this happens more often when sprinting and "falling" one block down, but regardless all fall damage is more or less broken.
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kumasasa
Duplicate of [MC-100]
Interesting. I tested this on SSP, and only got hurt by falling off from a 4 block height, however, when I joined a SMP server, I took damage from a 3 block height, and wasn't sprinting either. I think this has to do with a Player moved wrongly problem I heard from a friend when testing the snapshots, it could still be in the game, but who knows.