I don't think anyone is saying that you can't become addicted to bupe. People can become addicted, i.e. start using something obsessively and compulsively, to all sorts of things. It's definitely possible to get high from bupe. I have. But it's not likely that if used properly for the treatment of addiction that you will become addicted to Suboxone. If you start using it for recreational purposes that's a different story.
And there is a ceiling effect with buprenorphine that has been documented for decades, at about 32mg. Anything less than that will work like any other opioid. If you're on 16mg and you take more then yes, you will have an additional effect. If you are on 32mg and take more you should not get any additional effect other than maybe the placebo effect.
@CleanBreeze, you're right, you don't need to build up a tolerance with Suboxone but it makes little sense to take more than you need from the beginning. If someone could do well on 8mg why give her 16mg? In general th dose is adjusted upwards if needed. If your tolerance is low taking a high dose of Suboxone will get you high and that's not conducive to recovery.