Identify the protected alias affected by a proposed edit

internal/framework/validators/protected_terms.go

@@ -99,8 +99,23 @@ func validateIdentityPreservation(beforeByID, afterByID map[glossary.Identity][]
 	var selected string
 	found := false
 	for identity, beforeItems := range beforeByID {
-		if len(afterByID[identity]) < len(beforeItems) && len(beforeItems) > 0 {
-			if spelling := beforeItems[0].canonical; !found || spelling < selected {
+		afterItems := afterByID[identity]
+		if len(afterItems) >= len(beforeItems) {
+			continue
+		}
+		// Protect identity counts. Within an identity that lost a mention,
+		// use spelling counts to identify which alias was affected.
+		remaining := make(map[string]int)
+		for _, item := range afterItems {
+			remaining[item.canonical]++
+		}
+		for _, item := range beforeItems {
+			spelling := item.canonical
+			if remaining[spelling] > 0 {
+				remaining[spelling]--
+				continue
+			}
+			if !found || spelling < selected {
 				selected, found = spelling, true
 			}
 		}