@Claire, in Feb 2002, you created a topic where you mentioned soft deletes. While this isn't strictly related to Undo(Delete), this FEP recommends thinking of a received Delete as an instruction to invalidate the cache, and re-fetch, which would give you a better answer as to how to handle the received Delete or Undo(Delete).
Perhaps this might help.
Hi all,
Some discussion regarding NodeBB's handling of soft deleted posts and Discourse's parallel implementation prompted the creation of this FEP, which attempts to describe how the concept of soft deletion can be published without the introduction of new activities—using as:Delete as-is and relying on a backreference check for Tombstone in order to signal a soft delete.
https://codeberg.org/fediverse/fep/src/branch/main/fep/4f05/fep-4f05.md
