Thanks! I know the physics work kind of weirdly, but I just could't get them exactly right. It was my first time making a platformer (or submitting something to a game jam for that matter), so I didn't have a clear idea of how good physics should be programmed. I could probably improve them with a day or two of tweaking, but with the relatively slow workflow I have I simply ran out of time. The game turned out pretty coarse and unpolished but I appreciate that people played it and cared enough to leave comments, despite its flaws. Maybe I'll manage to make something better next year.
As for the WASD not allowing you to fall down, I only just realized that I assigned the "A" button to the "down" action, while it should have been "S".