In what countries do carriers charge for receiving messages? I know there are a few in Canada, but what else is there?

It's standard practice in the US if you don't have a texting plan, or if you exceed your limit. Sending and receiving both count equally.

On most plans offered in the US nowadays texting is included. All of the T-Mobile, AT&T, Verizon, Straight Talk, Republic, etc plans have unlimited texting included.

That's pretty recent, though, and a lot of people are still on older plans. Still, it's good they're finally gaining some sanity there.

Not really. 1 SMS = Request URL, so depending how many URLs do you request results the bill.

It appears the HTML of the requested page is returned to the requesting phone via SMS, which could be many many messages if you are loading say, a wikipedia page.

Most people in the world don't pay for receiving SMS messages. I think that is limited to the US and Canada and becoming less common even there.

Well luckily most people don't have to pay for receiving sms messages.

I know that in the past in US and Canada carriers billed incoming SMS, but I thought that alongside with the new age of messaging apps like WhatsApp and iMessage they dropped this nonsense. In Europe even when in Roaming there is no cost for incoming SMS.