The bridging as discussed in many threads, like you said is not supported and officially doesn't exist (even though it does)
The bridging is for the WAN port so you can use that WAN port as a standard LAN port so you can plug in five devices instead of four making the dir-655 an AP and switch only.
What you are looking for is wireless bridging, where the dir655 acts as a wireless client so that it connects to another wireless network. The capabilities implimented in the dir-655 does not support this, meaning the module hasn't been loaded and the xml style sheet hasn't been written to include the option to enable it.
However, if you HAVE NOT upgraded passed f/w 2.02 (i believe) you could plug in your phone or another wireless cell device, like a rocketstick and have the dir use IT to provide internet.
For the others I think I know what he is talking about.
He basically has an amateur observatory set up. He leaves his dir-655 and his telescope on top of a mountain connected to a ni-cad battery which is connected to solar cells (just kidding haha). So he can access his telescope from any where in the world and control it remotely and view the magical stars.
His USB server is part of this setup which controls the telescope and probably provides some interface for the telecope. This has nothing to do with shareport.
so his setup is probably like this:
telescope --- usbserver --- lan port 1 on dir 655
what he wants is this:
location 1 50,000 mil away location 2
telescope -- usbbserver -- lan 1 -- wifi link -- AP -> internet <-- modem -- Computer --'Tomb18 in his glory
So the only way you are going to get internet at your observatory would be with a cellular or satellite solution since you stated that the remote location does not have any Wifi available.
Plus since you stated that there is no wifi available at the remote location, your original intent is moot since the dir655 if it COULD be configured as a wireless client, would still need a wireless AP to connect to.