Just to reply to myself, but in helping out with a Flickr question over in the in-flight photos I found an easier way to get Flickr-friendly BBCode for linking to images:

this script ^

On the "all sizes" page for your photo, it adds an extra text box with the BBCode to display the image and have it link back to the Flickr photo page, per Flickr's rules.

Need to be using Firefox with Greasemonkey to have it work.