I wrote and awk script:
Export from Diigo as CSV tab-delimited
Clean up the file a bit, remove empty lines (mine had several)
Replace all ampersands in the URL's with & for URL encoding - it was quicker to just do that then figure out awk's gsub() issues with ampersands.
Run the awk script on the file and basically that was it.
My first couple tries I was getting errors because of the ampersands, but otherwise that's it.
./parse-evernote.ksh diigo.csv > diigo-export-full.enex
Here's the ksh script: