In message <4A2E5C73.2030509@kcl.ac.uk> Elena Pierazzo 
> I agree, also because we cannot say what <c/> is used for -- perhaps 
> some unconventional glyphs. In some manuscripts, for instance, there are 
> signs to mark the beginning of paragraphs or verses, that someone would 
> prefer to keep outside the <phr/> (which is a linguistic phrase). Or it 
> can be used to mark functional marks (carets, stars, etc.) for marginal 
> notes, glosses, etc.
> 

I think the recommendation would be to mark "unconventional glyphs" with <g>,
but in any case, let me stress that all of <g> <c> and <pc>  are members of
model.segLike, which is a subclass of model.phrase, and therefore allowed at any
level.