Question: full-width at

Question: is full-width-at the only character that contains the
at-sign in its compatibility decomposition?

If not, should we perhaps consider converting the entire e-mail
address to NFKC before splitting at at-sign?

Even if there are no other such characters currently defined in
Unicode, should we consider doing this anyway, in case a future
compatibility character has such as compatibility decomposition, or
can/should we avoid the issue by tying ourselves to a particular
version of Unicode?

And I won't even ask what happens if you try and follow the at-sign
with a combining accent.  I'm assuming there are no precomposed
characters of that form, so NFKC vs NFCD won't make a difference
here...

Actually, I will ask: assuming we just split at the at sign, the
domain name will begin with a combining accent.  How will IDNA treat
this?

	-roy