I write 5 zł (5 zlotys, 5 PLN) or 5€ (5 euros, 5 EUR) because in Europe we don't unnecesarily invert the currency symbol compared to what we speak. The following system, which I found on Wikipedia, would make the most sense:
Exceptionally, the symbol for the Cape Verdean escudo (like the Portuguese escudo, to which it was formerly pegged) is placed in the decimal separator position, as in 2
50.
That'd be perfectly consistent with what we speak and solve the problem of fractional currency notation as well.
The migration must be perfect, which means posts, comments and up/downvotes from the source instance must appear as if they've always been on the target instance.
Based Leo