Well, we think we understand what the writer meant by this question, but who knows?

"What can I do to make my keyboard more or less sensitive to aftertouch? I don't mean to change the response curve, just alter the physical sensitivity."

Sometimes an answer seems so obvious to us we can't be sure we really get the question (as a side note, it's a good idea to be very specific with questions). Basically the simple solution to aftertouch sensitivity is the sensitivity parameter in the keyboard or the individual patch. Any program that responds to aftertouch should be able to have its sensitivity to it changed without affecting the response curve. On the off chance that the writer is asking about the "feel" of the keyboard itself we would say that this depends on the specific keyboard in question. In the best case scenarios making significant changes to the way a keyboard action feels is a daunting and probably expensive scenario. You can try different springs (if you can find something that works/fits) and shims in the assembly, but it's really a pain and usually doesn't make a big improvement. The easy answer is to simply buy and use a keyboard that feels good to you. There are many excellent keyboard controllers on the market. The right one can really improve your playing and you can program sensitivity and curves into many of them so you don't have to do it on a patch by patch basic in the individual instruments.