Learn English – Does an object have “specificity to” or “specificity for” another object

Consider the following three sentences.

1. He raced out the door.
2. He raced out of the doorway.
3. He raced out of the door.

In the first sentence out is a preposition meaning 'through to the outside'. This is entirely unproblematic: he was in a room or building, and he raced out of it through the door(way).

In formal English the second sentence is equally clear: out is an adverb meaning 'moving or appearing to move away from a particular place, especially one that is enclosed', and the sentence means that he raced out of the doorway in which he had been standing. I shouldn’t be at all surprised, however, to find that some people use it synonymously with (1).

Since 'doorway' is one perfectly standard meaning of door, and since it is more than a little difficult to stand in a physical door, (3) is formally synonymous with (2). However, many people, evidently including at least one writer for Murder, She Wrote, use it synonymously with (1). For those people out of has in effect become a compound preposition meaning 'through to the outside' as well as the combination of adverb and preposition found in the formal interpretation of (2). I suspect that this, like in back of for behind, is more common in the US than in the UK. In the US, at least, it’s common enough to qualify as normal English, though there are also speakers like me who would never use it because it’s ungrammatical in their idiolects.

There are no special rules for rarely used prepositions. According to the Chicago Manual of Style, all prepositions should be lowercased (except when they are stressed or occur as the first or last word). But I hardly ever see this style used. The AP style is much more common. According to the AP stylebook all prepostions containing three letters or fewer should be lowercased, while the Wikipedia Manual of Style says all prepositions containing four letters or fewer should be lowercased.

However, the Wikipedia rules are not enforced, and as a result the capitalization on Wikipedia is a mess, and often in violation of the style manual (as you had observed). I think the reason for this is that the AP rules are dominant in real life, so this is what people are used to (i.e., what “looks right”). This explains many of the cases that you listed: down, over, unto, upon etc. are all capitalized according to AP style.

So regarding your examples, it depends on the style guide you choose whether the four-letter prepositions should be lowercased. Three- or two-letter prepositions like on, off, out or up should always be lowercased (if they are really used as prepositions and do not occur as first or last word). Yet should also be lowercased, if used as a conjunction.

There is no difference between book titles and song titles. The AP style for instance says that its composition title guidelines apply to book titles, movie titles, opera titles, album and song titles, radio and television program titles, and several more.