I have no way of measuring whether or not you experience feelings and sensations, or are just regurgitating statements to convince me of that.
The only basis I have for assuming you are sentient according to that definition is trust in your self-reports.
I'm fairly sure we can measure human "sensation" as in detect physiological activity in the body in someone who is under anesthesia yet the body reacts in different ways to touch or pain.
The "feelings" part is probably harder though.
> The only basis I have for assuming you are sentient according to that definition is trust in your self-reports
Because the other person is part of your same species so you project your own base capabilities onto them, because so far they shown to behave pretty similarly to how you behave. Which is the most reasonable thing to do.
Now, the day we have cyborgs that mimic also the bodies of a human a la Battlestar Galactica, we will have an interesting problem.