When aiming at a block which is outside of the world border, all right click actions are completely prohibited. For some reason, this also includes items such as fishing rods, snowballs, and food, which seems completely wrong. This is regardless of whether the player is in or out of the world border. If not pointing at a block but still at an area outside of the world border, the action can go ahead as normal.

Expected behaviour would be that any action can work on a block outside of the world border, unless that action modifies terrain, creates a (non-projectile?) entity which would be outside of the world border at the first tick of its existence, or deletes an entity outside of the world border.