Currently when Lexeme entity gets edited using wbeditentity API action summary contains ""wikibase-entity-summary-wbeditentity-update" message (in English it is "Changed an entity").
Items and properties have their dedicated messages (.e.g wikibase-item-summary-wbeditentity-update a.k.a "Changed an item".
It would be nice to have a Lexeme-specific message for Lexeme edits too.