Product: Tridion Docs 13.0.4630.2

When the user Jack is setting metadata of certain language object using desktop client, how does WriteMetadataPlugin capture the username Jack?

My situation: If Jack sets metadata (this metadata field is Language level) to certain language object, the WriteMetadataPlugin sets the same metadata to all language objects under the same GUID, but it causes recursive plugin calling, therefore I'm considering to distinguish from user-metadatasetting to plugin-metadatasetting, which requires capturing username.

(Given that the metadata field is not convenient to transformed into Logical level, nor convenient to set up a new Logical metadata field.)