I’m having a similar problem and it’s driving me nuts! I don’t use relative links, but I do copy a lot of links within my site. They are automatically changing to relative links, no matter what I do. I used both of these plugins, plus one called “Relative Link Fix”. None worked and the Relative Link Fix changed my links to http://http// on my site and feed.
I’m using WordPress on a self-hosted blog and Firefox. Does anyone have a suggestion to make sure the links are absolute, so they aren’t messed up in my feed?