Sorry, I think I've deleted it by accident when cleaning my dropbox ):
I tried doing it again but I couldn't reproduce the exact bug I first mentioned (where the character gets stuck in the middle of the platform rather than on top of it).
However, I found some new bugs, as well as the ones Jase00 mentioned. Not sure if I should post new bug reports or just post it here, so I'll post it here and if you guys want, I can make new threads (or add this to the ones Jase00 posted0)..
Anyway, here's the .capx:
In this .capx, the orange platforms are 32x32 sprites with the jumpthru behavior next to each other.
What happens is that the character automatically falls of some of the platforms when stepping on them.
<img src="http://i.imgur.com/X4D7eLb.gif" border="0" />
As for the red platform SOMETIMES the character is allowed to jump from the bottom of the screen directly to the top of the red platform, and sometimes he can't. He's not supposed to.
<img src="http://i.imgur.com/xWwbpdU.gif" border="0" />
edit: I forgot to mention the bug that Jase00 also mentioned, where if you stand on the top of the red platform, drop to the right and quickly press left, the Y vector will be set to 0. This happens if you touch any jumpthru platform while falling and miss the top of it.