Werner LEMBERG writes:
 > > Package inputenc translates the input characters that it controls
 > > into TeX code: ^^b9 becomes:
 > >   \show^^b9
 > >   ->\IeC {\i }
 > > Actually 4 tokens instead of one ^^b9 token.
 >
 > It is fairly easy to catch this case while the accent macro is looking
 > for its argument -- I just wonder why it is missing...

yes and no. it is "fairly" easy and it is also "fairly" dangerous in the sense
that it is likely to upset other parts of the process. don't underestimate the
kind of dependencies if you have to support all kind of extension packages and
not just those from a single user.

more importantly it wasn't ever needed in real life except for something like
\i (which wasn't at the for-front of inputenc chars as it was not generated
with the first keyboard layouts).

an even more important consideration is (or rather was) that it makes the
accent commands more complicated and slower.

these days speed is less an issue so it should perhaps be looked at again.

as far as documentation is concerned i thought that it is mentioned somewhere
that the accents need braces if input enc characters are placed into accent
commands but i may be wrong.

frank