clearly highlight Mysterious Portals when placed behind vending machines

I accidentally walked into one like this. It's a good thing I had 40 Inky Hoglanterns.

Vending machines are one of the only objects in the game that can clearly obscure other objects like this. Most of the other things like candles, fountains, etc, still leave space to see what's behind them.

 

This is a valid point.

 

Also doors.

 

And the bottom wall edges, traps show there but other things are hidden.

 

Ouch, yeah. Though on the other hand, it certainly makes the game more interesting... if deadly.