I've seen threads for 可以 as opposed to 会 and 能, but what about 可以 with its component, 可?
Wiktionary seems to use them interchangeably: 白银可以指：银，贵金属，用做货币时可称为白银
Is there a difference in nuance, or flow of the sentence?
"可" is a morpheme, while "可以" is a word.
With the meaning of "be able to", "可" and "可以" are interchangeable in most cases.
When we answer a question, we should say "可以", which means "fine", or "OK". When coming to popular culture, some of us would just answer "可", which is not literally supposed to. Say, if you answer like this, we could still understand.
Here are the situations I could come up with, only "可" is used as emphatic adverb (just like "very"), sometimes used to throw a question. See definition #2 here
"可以" simply means can, be able to. "可" means a lot than that, but is rarely used alone. It's wired that you say 可 to some questions. But it's ok to use like that, and when it happens, it has the same meaning as 可以, but it feels like u are a king.... Anyway it is really wired. when 可 is used with other character, it usually emphasis that char.