Philippe, > Just look at musical notations where a upper horizontal parenthesis > is used to group some elements (sorry I don't know how you name > it exactly in English or Italian), despite there's a measure break > in the middle, which may span to the other musical line: you end > up with two parts for the same diacritic broken across the lines.
They are called ties and slurs in English: http://www.ccarh.org/publications/reprints/ieee/STYPE1.HTM But they are *not* "diacritics". They are the representation of phrasing elements in musical notation, and as Michael indicated, their layout is outside the scope of the Unicode Standard, in any case. --Ken
