[thaumasiotes]

> Upper and lower cases have different significance

Yes, that's why they're a good example of assigning semantic significance to the font that something is written in.

> Well because I can have upper and lowercase letters in the same font.

What do you think that means?

Try this one: I can have Arial and Calibri letters in the same font.

Where a 'font' is a data file used by word processors to render ASCII or Unicode, it's just as true.

If you think a 'font' means something other than that, what is it, and how does your definition preserve the idea that a capital A and a lowercase a are distinct in some dimension that isn't their 'font'?