Diacritics do not work

[jorpic]

For example:

\dot{a} \dota a\dot
\hat{o} \hato o\hat

converts into

ẋ{𝑎} ẋ𝑎 𝑎ẋ
x̂{𝑜} x̂𝑜 𝑜x̂

In Unicode diacritics are combining characters but in s:presymbols they are listed as already combined with x.