No that is correct. Wt=mg . So you're weight equals your mass times the gravitational field strength. The field strength at the ISS is only marginally smaller than on earth, which in itself varies as you move around as evidenced by the fact that someone below used 9.81 as the strength instead of 9.82 as I would have. (Don't harp on about nude numbers, there's no point in including them here. ) So your weight is still the same a top Everest, at the dead sea or on the ISS.

Here's a question for you. A rocket takes off, why does its acceleration continue to get larger?

Answer: Its burning the fuel and exhausting it out the back so it has less weight to overcome, thus a greater unbalanced force. It has nothing t do with a decreasing gravitational field strength, the earths field reaches all the way to the sun and wobbles that a bit.

And I know perfectly well mass doesn't change, not need to capitalise it.

According to my physics teacher: 1. You weigh essentially the same in earth orbit as you do on earth, there is only a very slight difference. 2. When something is orbiting a planet it is moving so fast that it is falling around it. Imagine this,the ISS is moving really fast over a really flat large piece of ground, not a planet. It will eventually hit it. Now imagine that it is over a planet, it is falling towards the ground but as it is moving so fast,the planet is falling away before it hits it. So if you moved very fast indeed you could (disregarding obstacles and the whole friction thing, orbit a meter of the ground or less Yes as you can imagine, it was put far more eloquently by my teacher but that is essentially it. The reason I included (2) is just to clear up the whole weightlessness myth.