I would like to suggest that certainty and similar elements (certainty, precision and respons) be able to appear inside otherwise empty elements such as model.milestoneLike, so as to take advantage of the ability to use relative XPath in @match to point to a parent element (and some @locus of that element). (See http://purl.org/TEI/FR/2862151 for this feature applied to other "empty" elements...)
The specific use-case I have in mind is:
<lb n="13"><certainty cert="low" match=".." locus="location"/></lb>
I know you could use either (a) absolute XPath in @match, or (b) a stand-off pointer to an xml:id in @target, but since the functionality of @match exists, and there are occasions when it is very useful, is there any reason for it not to be available more globally?