Student,
As you noted, the FAR permits you to log as PIC that time for which you are the sole manipulator of the controls. That is a different question than whether you can log actual or simulated, though. You are supposed to log the conditions (actual, simulated, etc.) associated with the instrument time. If you are PIC, as in the sole manipulator of the controls, in an airplane for which you are rated (category and class--ie: Airplane, Single Engine) and you are in actual IMC, then you log it as actual. If you're under the hood, it's logged as Simulated.
Your flight instructor may ALSO log this flight time as PIC, and also may log actual.
You do NOT have to be instrument rated to log actual instrument time, or to fly in actual IMC, but there does have to be SOMEONE aboard at the controls who is an instrument rated instructor.
Here's another similar example: Let's say you are a Private Pilot, Single Engine Land rated. You are working on commercial maneuvers, so you rent a Cessna 182 R, a complex aircraft. You don't have a complex endorsement yet, nor do you have a high performance endorsement. Nonetheless, the FAA Chief Legal Counsel says you can legally LOG your flight time with an appropriatetly rated CFI in that airplane as PIC. The logic is that you are RATED FOR AIRPLANE, SINGLE ENGINE LAND and that's what you're in. You can LOG PIC in that airplane, but until you are endorsed to serve as PIC, you cannot SERVE as PIC.
Confused yet?
MTV