We’re testing with Comic Jens, which contains many combining diacritics and pre-composed characters. Some pre-composed characters for which Comic Jens has a combining diacritic are missing from the font, however. This includes, e.g., the combining dot above (◌̇, U+0307) and precomposed characters Ȧ (U+0226) and ȧ (U+0226).
A Á Á ← notice different “A” shape for both cases!
a á á ← a+ ́ obviously replaced with pre-composed á
K Ḱ Ḱ ← Comic Jens does not contain pre-composed Ḱ
k ḱ ḱ
A Ȧ Ȧ ← Comic Jens does not contain pre-composed Ȧ
a ȧ ȧ
C Ċ Ċ ← but it does have a pre-composed Ċ
c ċ ċ