What about capacity consults in the hospital? Involuntary treatment doesn't only come up when it comes to psych admissions and most of capacity isn't actually determined by psychiatrists. What if a person is refusing to eat, cachectic, refusing a g-tube, but is clearly delirious and can't reason?
Interestingly, the bar for involuntary treatment is actually set higher in psychiatry than it is in the rest of medicine. In medicine, you just have to show that the person doesn't have the capacity to make the decision. In psychiatry, you need to show that they are dangerous. It can lead to some interesting situations where a psychotic person who isn't threatening himself or anyone else can be treated against his will for a medical condition, but not for his psychosis.