So here's my attempt to explain ice breaker in one place objectively. It makes no stance on whether it should be included in NMG, or even whether it should be considered major or minor.
- Door state walking allows Link to walk 1 pixel past the door inside of collision
- Retriggering the doorstate allows Link to walk through collision, as the door movement forces him right
Neither of these is new as a glitch. #1 was just considered useless, but as a fun oddity could be used to clip the hookshot.
#2 was very interesting, but limited to applications in hacks and TASes. For example: This room is completed by holding v to exit the door and safely walk over the pit, then holding < into the other door. The intended solution is hovering.
While this glitch involves a door, it is not a door glitch. Door glitch is just a bad name for transition corruptions specifically in the underworld. Door glitches encompass death hole and all known underworld wrong warps, neither of which need to involve literal doors.
The opposite of this glitch is already abused for minor time saves. Bastard doors can be used to deactivate the door state, and place items while physically inside a door.
The somaria block is not used for any corruption, it is simply there as a stopper. When Link moves left, he moves 2 pixels into the door. When the block's code activates, it calculates that the block can't move, so Link shouldn't move either, and it sends him backwards. The somaria block pushing Link back out of the door does not account for the tile change that occurs. It's not been looked at extensively, but it likely does account for it from the 2nd frame onward.
What we're clipping
As far as the game is concerned, we are not clipping a wall. The game code sees tiles by ID, but makes no judgement on what they are in human speak. It sees ID and matches it to some behavior. Existing editors (HM and ZScream) refer to this object as a rail. An all encompassing answer based on objective facts will fail to satisfy all concerns or cases as far as what the object is.
Also, from the game's point of view, tiles are 8 pixels, not 16. Every tile is treated independently, and the game doesn't pay much mind to how they are grouped together in most circumstances.
Comparison to other allowed clips
A lot of people have compared this to hammerjump, but when making this comparison, hammerjump is considered a rail clip. Technically, it's a pit clip. When near a pit, collision may end up ignored. This oddity is part of the spectacle rock bomb jump in 100%. For hammerjump, while the object being clipped is considered a rail, it would be impossible without the assistance of the pit. The corner of the platform gets in the way, and it can't be clipped as other rails can (such as Tower of Hera). These types of clips are due to the collision being only 8 pixels.
In these clips, the only thing actually "ignoring" collision is the hookshot. Once the hookshot has decided to pull Link, the objects between Link and his destination are not even considered. This is based on the assumption that the hookshot's path will always be valid.