I was a little worried that that inconsistency in what objects were solid for the ghost would be frustrating to players, but I didn't really have a better answer to how to lay the stages out the way I wanted to. In the end, I figured that, since there's no penalty while not possessing, it probably wouldn't make a huge difference if people spend a couple seconds trying to jump on some thing that they can't get on. I think given a little more time, I'd hopefully realize that I shouldn't put thing that you aren't able to jump on next to objects in the environment that you have to find a way on top of. That definitely sends the wrong message.
With regards to the bit in the top left, how/where were you stuck? There's an I-beam back there that you should be able to get out on, though I didn't spend a large amount of time testing all the corners to see if there were issues back there.
As for interactions between different hazards, I have a million ideas on things to do with that. I just didn't implement any, because it would've been super time consuming and difficult to balance in terms of difficulty. I did want to have the bees spread to other people and the fire spread to other people and wooden objects, but I just never got around to it. If I continue working on the game, I'll definitely make sure to get that stuff in there. And that idea with the oil leak is really good!
Thanks for the in-depth feedback and suggestions. They're really appreciated. :)