Feedwordpress is a WordPress plugin which allows easy syndication of RSS-feeds to your blog, sidebar or both.
In Feedwordpress you are presented with the choice between linking to your local post when a excerpt is imported or linking directly to the remote site.
Often you will want to present a link to the original post, but also allow visitors to comments (and ping) on your site. The setting ‘ Point to local comment feeds on this website’ doesn’t seem to do much if you point your permalinks to the original site. This is a quirk which held many, including me, up for a few hours.