I would like to propose a change in the way the greek-ibycus4
input-method for ancient Greek handles capital letters with iota
subscript (ypogegrammeni), as a result of having been bitten by its (to
me) very surprising behavior.

Currently, when you type a capital letter followed by a normal iota, the
input method arbitrarily decides that this must actually be a subscript
iota.  But in the vast majority of cases, this is not what the user
intends at all -- he or she wants a normal iota after the capital
letter.

The reason for this ambiguity is that the ibycus4 encoding for LaTeX
does not actually support subscript iotas under capital letters (it
expects you to write them adscript, as if they were normal iotas).  So
there is no pre-existing standard to appeal to, but it seems logical to
use the | character after the vowel, just as for lower case vowels.

In other words, with the current code:

    )Ai => ᾈ 

which has two problems: (1) it is very surprising, and (2) there is no
straight-forward way to type the common sequence of Greek characters Ἀι
‐‐ you have to separate the vowels with a space and then go back and
delete the space between them.

With my proposal:

    )A| => ᾈ 
    )Ai => Ἀι

Now there is an easy way to type both sequences and the default behavior
is much less surprising.  It's also consistent with the behavior of the
greek-babel input-method.  Patch attached.