I don't count Wifi (ad hoc or otherwise) as tethering, strictly speaking -- although I know everyone uses the word as they please nowadays, which accounts for much of the confusion in those forums topics :-)

As Ayle said, I was referring to the classic notion of USB or Bluetooth DUN, ie using the phone as a modem indeed. Like I did with past and present phones, my various Maemo tablets, my Windows & Linux notebooks, etc.

And yes, I now understand it is deemed "not possible" with Android. I just can't believe it, is all :-)