If someone has spilt coffee over my couch, can I say "who has been spilling coffee over my couch?!", using the present perfect continuous to complain?
It all depends on the frequency of coffee spilling on your couch.
Let's say that you walk into a room and see coffee all over your couch. If this is abnormal, you would probably say
Who spilt coffee all over my couch?
since the action happened once.
If you walk into a room the next day and see more coffee all over your couch after you just cleaned it, you would probably say
Who has been spilling coffee all over my couch?
Who keeps spilling coffee all over my couch?
since the action has happened multiple times.
You use the present perfect continuous when you refer to actions that started in the past and are still going on. If the action isn't continuing into the present, it's best to use the simple past.
You can... but why?
Continuous tenses suggest either temporary conditions, actions that are spread over time, or repeated actions. Using the past continuous with a sudden event like "was spilling" suggests repeated actions in the past.
You probably just want past simple "Who spilt coffee on my sofa?"
There is the fairy tale of the three bears, and when they discover that some of their breakfast has been eaten, the father bear says
Who's been eating my porridge!?
This is appropriate perhaps because some porridge is still left, so the action was temporary and since it wasn't completed it must have been spread out in time.