Once you enter a player's housing I think it would be useful to have an automated message sent in your chat as reminders such as "You can do /house for a list of housing commands" (only on your own housing though), as well as "You can do /worlds to leave this housing and join a world." Specifically for newer players, this could be helpful as newer players might not be aware of the housing commands and/or a way to leave housing without using a warp key bag and losing their location.