In https://www.wikidata.org/w/index.php?diff=770442639 I changed the gloss from "bar" to "foo"
Now https://query.wikidata.org/#select%20%2a%20%7B%20wd%3AL123-S8%20%3Fp%20%3Fv%20%7D%0A includes two skos:definition triples for the same language, the old gloss and the new gloss.