When an alias hasn't been filled yet, an entry in the text of a book gets replaced with the string "[...]". After filling the alias (with an actor via Papyrus, in this case), it gets replaced with the full name of the reference. However, after Clear() is called on the alias, the text replacement "sticks" as the last name it was set to, and does not reset to "[...]". Filling the alias with a new target properly updates the text again to the new name, but is there any way to "reset" this text back to its unfilled value... short of creating a dummy object and actually giving it the name "[...]" to fill the alias?

did you check "clears name when removed"?