It makes even more sense to have a universal symbol to indicate a feed. From a usability perspective, I agree that all feeds should be represented by clicking this icon - although perhaps the responsibility should rest with the tool used for reading feeds.

Another usability issue I have been thinking of is that you and I know what these feeds do, but the everyday person may not. Therefore, what might be interesting is to somehow embed code that would automatically add the feed to a person’s default feed reader, whether it be a local program or an internet application. Think of it as setting the “this application will open with” type scenario once there is recognition of xml. Therefore, with the touch of this universal icon, a user will know that the feed will be saved on his/her default reader, perhaps promoting a pop-up for additional identifiers.