But, again, he was in the UK buying US stamps, so that the FSF could mail their answer back to him from the US. I don't think UK post offices supply all the world's stamps, buying that online from individuals who have them for sale makes some kind of sense, doesn't it?

I guess the a more "digital native" way would have been to first check if the USPS supports some kind of downloadable/printable stamping method, like QR codes or pre-bought labels (which, according to come early comment, they do).