So, @fiatjaf, the founder of Nostr, now uses a client which randomly adds meaningless "e" tags of type "mention" when he replies to a thread, pointing to some previous item on the thread.
The standard thing for a client to do when displaying such posts would be that of showing the referenced note as a quoted note. I don't think this is the intention.
Why do client include tags that make no sense?
See this posts for instance:
View quoted note →
View quoted note →
View quoted note →