My original preference was for all potentially 20 bit code points but there was considerable push back on this in the review thread due to the multiple encodings Unicode allows for "the same" character. I resisted it for a while but conceded it was best to stick to "just ASCII". I don't know what the solution for EBCDIC would look like (which arithmetic on code points make absolutely no sense at all as letters and numbers do not have sequential code points) and that's not a problem I'm trying to solve at this point.
The utility of Single Quoted literals is partly aesthetic but primarily as a more convenient syntax for UInt8(ascii: "\n"). The arithmetic is an unfortunate side-effect of the integer conversions though it has its uses.