I consider the "reply" as "event"

An "event" can be a "Reply" but also an "information reporting on event"

Exemple "Item delivery"

Sometimes, TECH needs to add an event (reply) between 2 replies

ONLY FOR TECH & ADMIN, add a little "+" icon displayed between the replies.

The date & time linked to this reply will be for sure the date & time of registration of it.

If it's not user friendly (participate to too much info on screen), this could be displayed only when mouse is moving in the area between the replies