That’s both mean and strange.

What possible gain could there be from excluding the UK and (seemingly) allowing access in continental Europe?

IIRC, (a version of) The Daily Show is broadcast on UK television. We wouldn't want competition now, would we?

Indeed. It's shown on the digital terrestrial channel More4 the day after broadcast, as well as available online via 4OD. Sadly, The Colbert Report is also blocked and that's not shown in the UK.

Comedy Central is broadcasting The Daily Show here in Germany. CNN, too. A crappy cut-together version, but still.

Because someone owns the exclusive rights to the Daily Show in the UK and no one does in Germany.

None. For people who don't know any better, they just hit "Back" and a visitor is lost. For people who know better, they connect to a VPN quickly, watch the video, then hop back off again :-)

Looks like they're blocking predominantly English-speaking countries.

I'm seeing it fine in the UK. There's a bit of firefox configuration to do first, but I got around to that a few months ago, then forgot about it - it just works now. You can probably find it if you google.