If an admin partially blocks a user from Harrison Ford (Q81328), currently they wont be able to edit the claims on that item. However, they will be able to to add/remove the item from other items. For instance if they want to edit the cast of Star Wars (Q17738) they would be able to add and remove Harrison Ford (Q81328) from that list.
Should partially blocking an Item also block referencing that item? What about the Qualifiers? The References?
The way this would work, is if you go to add/edit/remove a claim, Wikibase would execute User::isBlockedFrom on the entity they are trying to edit Star Wars (Q17738) as well as the reference of the item they are adding or removing Harrison Ford (Q81328). They must not be blocked from either in order to make the edit.