[vbezhenar]

domain name and protocol name is case-insensitive.

If you care about QR code size, you should use URL shortener service which you can program in whatever way you need.

So I don't think that's major restriction.

[Xss3]

Then your qr code only works if the url shortener stays online.

In many cases its wiser to roll your own permanent shortened urls so you aren't beholden to a third party service.

[vbezhenar]

Of course you can roll out your own URL shortener. It's not a problem to buy short domain.