Per https://en.wikipedia.org/wiki/Wikipedia:Deferred_changes, when a user's edit is deferred actively (i.e. in such a way that it is not visible to readers), the user should be notified. The user should also be notified when their edit is accepted, but that's covered by {T54510} (see T54510#2875256 for screenshot).
The implementation that's currently being worked on [[https://gerrit.wikimedia.org/r/#/c/316957|this patch]] looks like this:
{F5057490}
The first notification is shown for edits that were automatically deferred because they matches an AbuseFilter rule. The first secondary link ("AbuseFilter") links to a documentation page about AbuseFilter (if the edit was deferred by ORES, the first secondary link will say "ORES" and link to a documentation page about ORES), and the second one ("Help") links to a documentation page about deferred change.
The second notification is shown for edits that were deferred by a bot (or human). The first secondary link is the user who deferred the edit.