2FA, you get a popup in your bank app asking "Do you want to pay X euro to Y?" for online payments. Can turn that off if you want, but it isn't a big bother.

That‘s not how direct debit works. There is no accountholder involvement with processing direct debits, but they can be easily reversed (although after the fact).

There are related payment schemes though that do initiate a push payment (i.e. SEPA credit transfer), giving the accountholder control over the amount and payee, but they are not yet as ubiquitous or usable internationally.

That is exactly how my debit card transactions works. When I buy a game on steam using my debit card I get a popup in my phone asking if I really initiated the payment and lets me decline.

The payment page spins until I click ok on it in the phone, since my bank wont accept the transaction otherwise.

The grandparent post was asking about the German payment system, which presumably refers to SEPA Direct Debit, not debit cards.

What you are referring to is called 3DS, and it's a feature of both credit and debit cards. (It's available worldwide, but most commonly used in the EU, since it's mandated for ecommerce card transactions in many circumstances.)

It also only happens for higher-value transactions here. I don't have to authorize every tenner unless it's the 10th in a row or something

I don't know how it works in Germany, but in the Dutch system, iDeal, I see the amount I'm authorizing. Of course if I'm sloppy and rapidly clicking through my bank's screens, I might not notice it if they changed the amount at the last moment, but any merchant that can be shown to do that would probably be in a heap of trouble.

I do think it's possible to authorize an unspecified amount; automated gas pumps seem to do that, but they seem to be the only ones, and it probably has a hard maximum.

Of course any PIN transaction that goes through the merchant's equipment is not quite as secure and relies on a level of trust that's not necessary for online payments, where I give my authorization through my own bank's website.

In the Netherlands the customer picks theirs from a list of banks on the iDEAL website then the transaction is done on their banks website. Other services can be fit in front to extend the choices with other payment processors.

shop [> mollie] > iDEAL > ABN > shop

or

(pc) shop QR > (phone) photo app > iDEAL > ABN

If they do that (via direct debit), I can click a button in my online banking interface, immediately get the money credited back, and the merchant is debited that amount plus a fee.