The page in the Guidelines on Type of Text describes three competing encodings for this feature. I think EpiDoc should come to a conclusion about which to recommend forcefully (or come up with a fourth, better one?). I have no strong opinions about which is most appropriate, although I know it's been discussed repeatedly. This should probably be surveyed on Markup, or at the very least discussed with some TEI-active friends, before making a decision or proposal.
This has been discussed again on Markup recently (See thread) but as yet with no conclusion. Opinions there or here welcome!