Regarding the Oxford comma, I submit that the precedent with grammar and spelling is that where a rule is sometimes required for clarity, it is generally applied universally*. The capitalization of a name, for example, is rarely needed for clarity, but there are some names which can also be other sorts of words (Pat is the first one that comes to mind, and the difference between Mother and mother...), and yet we capitalize all names. Same for the capitalization of the first letter of a sentence, which is redundant with the full stop in most contexts, except where an abbreviation is used. As such, I argue that the Oxford comma should remain in common use, based on precedent if nothing else.
That said, I agree that including the Oxford comma on that coin would look more like a minting error than an intentional mark, so perhaps they should have changed the design to have the alliteration around the border or something like that? But, if anyone wishes to participate in the boycott, I would be happy to receive all the 50p pieces you wish to send me!
*Except, of course, that there are exceptions to just about every rule in English...
