Variant positions of combining marks

[Peter Kirk]

Does anyone know of any cases where the same combining mark is combined 
with the same base character in two or more different positions, and 
where the positioning is semantically significant? How does Unicode deal 
with this situation? Would variation selectors be appropriate in this 
situation, or what other mechanism might be proposed?

I am looking for examples other than Hebrew vav and holam, because I am 
looking for precedents for dealing with this situation elsewhere in 
Unicode. I am also excluding distinctions like DOT ABOVE and DOT BELOW, 
where the marks are treated as different characters although the glyphs 
may actually be the same.

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Peter Kirk
[EMAIL PROTECTED] (personal)
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http://www.qaya.org/