Earlier quoted context omitted.
As English is not my first language, Elements of Style really has done a decent job of highlighting things that I either completely missed back in my English education, or was not covered at all.
I struggle mightily with "on"/"in". It's a funny thing; English native speakers will tell you that there are rules: "in" is for "inside" and "on" is for "on the surface", as simple as that. But almost every use I can think of is ambiguous. Is that smile in your face or on your face? Are you sleeping in your bed, because your mattress closes over you like the insides of a bag, or on your bed, because it's just a woode…
Things go in a CONTAINER. Things go on a SURFACE.
Then there's FURNITURE, which does both but not really. People sit on a bench, but they sit at a table. Only Things sit on a table. People sleep in a bed, but all Things sit on a bed.