I have found that it is possible to clip through a wall in the Forgotten Keep using pots, based on the fact that if a pot is placed against a fixed object (like another pot) it will push the player back, as below:
This skips using the key from that chest to unlock the gate below that platform, so gives us another spare key for use later in the run. It may save most time to use it in WEK so the skip in WEK using the rift spell can be used (as we would not have to worry about missing out on that key). Alternatively, the first key in Frozen Temple takes well over a minute, so skipping that would be useful.
I should add that this glitch is very easy to get wrong. Often when placing the first pot in the chest it will fall through the floor and break, failing the glitch (as there are only two pots to use on that platform). I am still toying with the set up to try and make it consistent, but it may be fairly precise.
Some other thoughts occur to me: (i) There may well be other places where wall clipping is possible with this technique. (ii) Further, it may be possible to do this to clip through gates and/or other solid objects. (iii) You will notice that soon after the clip into the wall the player transitions to the next screen/area, but not because the player has gone all the way to the right of the screen. This suggests that possibly as soon as a solid object is clipped into, the game will automatically throw them into the next area. If true, this could open up a lot of potential skips.
I have not experimented with any of this as yet beyond what is seen in the video.
Edit: One very consistent way of getting the clip in Forgotten Keep is to grab the pot just before the big swinging axe, and if you jump as late as possible your are able to make it (holding the pot) onto the platform with the chest. You then place a pot to the immediate left of the chest and then grab a second pot and place it on top of the chest. You can then grab the third pot and complete the clip. Image below: https://drive.google.com/file/d/0B3hRqcfMGu5aRFl0MHNfUWd6TDg/view?usp=sharing I have found a few more places where clipping is possible but the character just falls to the bottom of the screen and dies. Unfortunately I think this glitch may only have a use in this one spot, in the Forgotten Keep.