RSS Feed and NameSpace

I am trying to resolve a problem with my site posting to Facebook. As part of my troubleshooting I found that the RSS feed has some issues. I thought I should fix these before continuing to TS the Facebook issue. I have solutions for everything but Feed Validator has this issue:

line 28, column 0: Use of unknown namespace: com-wordpress:feed-additions:1 (11 occurrences)

I can’t seem to find a solution to this one. The feed validates and I doubt this is causing the problem with Facebook. But I don’t understand it, don’t know how to correct it and can’t find any reference to it in settings. I am running a Managed WordPress site if that makes a difference.

I done the disable plugin thing.

My Website: http://ronsamazingstories.com
The RSS feed is: http://www.ronsamazingstories.com/feed/

Thanks for reading,

-Ron