On the substance of these rules, my conclusion (and Denis knows this are better than I, so can amend this) is the primary difference between what Chicago calls "American" punctuation rules and "British" is that the former puts trailing punctuation within the closing quote, and the latter does not, except in rare circumstances.
This is independent of citations, BTW. It's just that the citations expose them when we have to switch between different styles. Given this, we could imagine a default function that itself took a parameter to address that difference, with possible values like "inside-punctuation" and "outside-punctuation," which of course would be more general than calling them "American" and "British". But those are among those "details" I noted in my previous message. The function would be pretty close to the logic of what Nicolas already wrote, but with some additional logic to deal with the "British" case. That would give pretty robust and flexible support out-of-box. But allowing one to plug in a different function would give still more flexibility, of course. It could well be my characterization of the fundamental difference between those two punctuation rules breaks down in other cases. Bruce
