...the original issue of _whether or not there should exist Unicode characters for which IsDigit() returns true and for which GetDigitValue() returns values in the range ten to fifteen_.
If/when Tengwar gets coded, it will have digits for 10 and 11, as it uses base-12.
I imagine the Dozenal Society would also be grateful for 10 and 11 digits; they've been using X and E, or more recently * and #, for such things. I would say that to the extent that all this is a good idea, we shouldn't code lots of different ones (A,B for the computer crowd, X,E for the Dozenal crowd); let glyph-variants handle it.
I might also point out 2160-216F, which could be considered something of a step in this direction, with appropriately tailored software.
(as an oddball addition: if the maximum base we're really trying to support is 16, it might be handy to have a "16" digit as well, even though base 16 doesn't use it. Since, as Jill says, a digit is a digit, this would enable us to specify the base used for another number *unambiguously* all the way up to 16. It's something I think is missing in Lojban, which has digit-words through 15; a 16 would have been helpful.)
~mark
