Add clarifying comment

import/marc_local.properties

@@ -85,6 +85,10 @@
 #   characters to exclude (regex)
 #   transliterations
 #
+# A work key will be generated for:
+#   each uniform title field
+#   each combination of a title field (both with and without non-filing characters) and author field
+
 # See
 # https://unicode-org.github.io/icu/userguide/transforms/general/#icu-transliterators
 # for more information on the transliteration rules.