Well, I thought that I had trackback working, but it turned out that I had a bit more work to do. The default trackback ping url was causing trouble – it worked as a GET and failed as a POST. And since Radio does a POST, I was unable to ping my own weblog.
While I was inside Radio, I also redefined the meaning of the trackback.flEnabled and trackback.flAddTrackbackLinks preferences. As Radio ships, flAddTrackbackLinks is ignored if flEnabled is false. With my modification the flags are independent – flEnabled specifies outbound behavior and flAddTrackbackLinks specifies inbound behavior. I’m biased, but I think this makes much more sense.
Unfortunately, I was forced to modify existing functions and I’m sure this will break at some point in the future. So here is the list of modified functions, where I have a chance of finding it again: