I can't really explain this, but I am pretty sure that hand-knit underpants will be as wonderful as hand-knit socks are reputed to be (and I mean to find out about that first-hand, too). These are fresh off the needles, just out of the laundry-spa treatment, and I shall be test-driving them at once.
It's a cotton-linen blend, because that's what I had enough of for a reckless experiment. You have already noticed that the 'right' side of the stockinette stitch is facing the interior, because it should be slightly comfier and less waffle-impression-giving that way. The cables around the edges look great - not sure how we'll they'll work in practice. Queuing up my next pair in a cotton/wool blend - should be lighter and springier. (And I have enough of it for a slightly more informed, less reckless experiment.)
And no, I haven't been knitting exclusively since last you've read here. But thanks for asking.