Mostly for myself this one:
UPDATE and DELETE considered harmful for OLTP. Everything can be captured with INSERTion of deltas. (Ref: Journaling).
Timelines. Very useful.
Revisionism is bad. See note about UPDATE and DELETE.
Interesting parallel with source code control systems.
To recapitulate: Everything can be captured as a delta and a reason, including correction of errors. Don’t use UPDATE.