All of the spacing combining marks (general category Mc) except musical symbols have a canonical combining class of 0. So, for example
0B95 (TAMIL LETTER KA) 0BC7 (TAMIL VOWEL SIGN EE - stands to the left of the consonant) 0BBE (TAMIL VOWEL SIGN AA - on the right) is canonically distinct from 0B95 0BBE 0BC7 - even though I presume that they would generate an identical glyph. Why is this? The Canonical Combining Class Values in UCD.html has entries and values for left attached and right attached - but no characters have these values. - Tim
