I recently upgraded to Thunderbird 1.5 and it looks like other people are in the same situation in regards to the full text feeds. The data is hidden in the content:encoded section.
Some thoughts about Scoble – wakeless.net
His feed has changed and it doesn’t appear to be a fulltext feed in Thunderbird I’ve looked at the feed and I know the data is there, but I can’t see it. I wonder how many other people this is happening to.