I have placed a table with a chair in some bedrooms so that my colonists can eat their breakfast at a table.
now, however, it often happens that one colonist is still sleeping and another one enters his room and sits at the table.
in my opinion, colonists should only go into someone else's room if they have a job to do, or if the person is a friend of theirs and awake. otherwise it would be nice if they knocked.
This actually seems like it'd be relatively easy to put in, similar to how prisoner-beds / -rooms / -objects work. i.e. The prisoners get ownership, although the player can right-click to override pawns respecting that ownership, to eat, equip, use, etc those things. Any object or furniture in a bedroom gets shared ownership with all pawns who have beds in that room.
This doesn't exactly fix the problem, but you can build bedrooms around a central dining area (doesn't have to be the only one). This way, pawns will eat their meals at a table when they wake up, but won't disturb each others' sleep. Doesn't fix the issue with creepy art admirers though.