That only works in one direction. You can use it to connect FireWire devices to a computer with Thunderbolt, but you can't use it to connect Thunderbolt devices to a computer with FireWire.

Contrast with USB. I can go out and buy a USB storage device brand new off the shelf in 2015, plug it into an iMac from 1998, and it will work. It will be slow but it will work out of the box.

I don't have a thunderbolt device yet, but I wouldn't expect the behavior you're talking about. Being able to connect my old firewire devices might be nice, but I wouldn't expect to be able to use new devices on an old port.

There's no reason to expect it. But USB does it anyway, and it's really nice to know that I can buy USB 3 devices and use them with my USB 2 computers as long as I don't need top performance.

He said he was "out of luck completely". He's not.

That comment is entirely about using newer peripherals with older computers. He is.