I keep coming back to the line in Appendix B that says the scope ceiling is calculated differently from the visibility ceiling, but does not explain why. If I had to guess, it’s trying to patch these weird behaviors that are ultimately caused by a mismatch in the world model.
Consider this:
>open dumpster then put orb in dumpster then close dumpster
You open the dumpster.
You put the glow orb into the dumpster.
You close the dumpster.
>put rug on lid
You put the rug on the dumpster's lid.
>stand on lid
You get onto the dumpster's lid.
On the dumpster's lid you can see a rug.
>l
The dumpster
In the dumpster you can see a glow orb.
>x orb
You can't see any such thing.
>x rug
You see nothing special about the rug.
>x lid
On the dumpster's lid is a rug.
>stand on rug
You get onto the rug.
>l
The dumpster (on the rug)
In the dumpster you can see a glow orb.
>x orb
You see nothing special about the glow orb.
>x rug
You can't see any such thing.
>x lid
You can't see any such thing.
>exit
You get off the rug.
The dumpster
In the dumpster you can see a glow orb.
>exit
You can't get out of the closed dumpster.
When standing on the lid, I can examine the lid and the rug, but not the glow orb. However, the glow orb inside the dumpster prevents the lid from being in darkness. and look acts as though I am inside the dumpster.
When standing on the rug (on the lid), I can examine the orb, but not the lid or the rug. Look acts as though I and the rug are inside the dumpster.
When I exit the rug, I enter the dumpster itself, not the lid. (Note that the dumpster is closed and not enterable.)