Well, it looks like my "stiffer" trackpad is the result of Apple's having addressed a longstanding issue.
When I got my first MBP with glass trackpad close to four years ago (but bear in mind that the machine was already three years old when I bought it) I was infuriated by my cursor's frequently jumping around my screen when I tried to place it: attempting to insert it into a body of text often resulted in its winding up it in the wrong place, even selecting text I had no intention of changing, which resulted in its being overwritten when I began typing without realizing that it had been selected.
The "Geniuses" gave me a new trackpad, but they were perplexed when the exercise proved useless.
I finally got a good answer from an AppleCare tech who figured out that because I tap my trackpad with the side of my thumb, rather than its tip, it was picking up spurious input.
Great! What the hey do I do about that?
My solution was to attach (with two-sided Scotch Tape) plastic cut from the lid of a to-go container to strategic portions of my trackpad, and it blocked the spurious input flawlessly, but when I upgraded to Sierra 10.12.0 I found my trackpad practically unusable because it was much stiffer than it had been, which necessitated my removal of the plastic, which left me with a still-jumping cursor...my primary reason for reverting to El Cap.
Fast forward to Sierra 10.12.3 in which I found my trackpad even stiffer than it had been the first time I upgraded.
I removed the plastic again, and this time... VOILA!
I'm assuming that Apple has tuned down the trackpad's sensitivity, that the stiffness results from its not getting sufficient input through the plastic, and thus its improved functionality without the plastic.
I can't say that the fix is 100%, but it's close enough that I can live with the occasional jumping - but no unintended text selection - with which I've been dealing.
Thank you Apple!
