IJ with accent

[a.lukyanov]

28.09.2016 22:33, Michael Everson wrote:
> The right way to do this is to follow the ligature (capital or small) with U+0301 and then have your font draw two acute accents on the ligature.
>

That seems good, still the Unicode standard says nothing about it. And 
doubling a diacritic is not quite self-evident.

It would be nice to have an explicit description of this issue somewhere 
in the "Europe-I" section.