A couple of days ago I ran this to get a candidate list of erroneous defs which should have been quotes:

xquery version "3.0";
declare default element namespace "http://www.tei-c.org/ns/1.0";
declare namespace util="http://exist-db.org/xquery/util";

for $t in //TEI
for $e in $t//entry
let $quoteSegs := for $s in $e//quote/seg where
string-length(normalize-space($s)) gt 0 return translate(normalize-space($s), '*', ''),
$defs := for $d in $e//def/seg where string-length(normalize-space($d)) gt 0 return translate(normalize-space($d), '*', ''),
$dupes := distinct-values($quoteSegs[.=$defs])
where count($dupes) gt 0
order by util:document-name($t), $e/@xml:id
return concat(util:document-name($t/@xml:id), ' / ', $e/@xml:id, ' : ',
string-join($dupes, ' | ')) 

I've now written XSLT (utilities/flag_superfluous_defs.xsl) to insert a comment before each of these candidates.