Still true with the Solr-based storage: event if Event have a DocumentReference, the Locale part of the reference is completely ignored by the storage (it's serializing it using DocumentReferenceConverter, which does not take into account the locale).
This message was sent by Atlassian Jira (v9.3.0#930000-sha1:287aeb6)
If image attachments aren't displayed, see this article.