Now, here's what i did:
I clicked on the curved arrow icon at the bottom right of your picture, selected BB Code and the size I wanted, then highlighted the string that comes up in the box below. I copied that string.
Then i come to here, selected the picture icon from the posts toolbar (above, next to the one that looks like cinefilm), and selected 'From URL'. I pasted the string into the box, and unticked the tick box below it.
When you click Upload, you get the following string, between
Misty water 2 by
aaron.rumney, on Flickr
Now delete everything except the bit in red, and ensure you still have the
at either end, and your image should appear.
It is a bit of a faff to write out, but it is pretty quick really.