Marty, your personal activity feed is people you are following, images commented on, favorited etc. Community activity is just that and everyone sees that feed.
it's just for you. the people you commented on, watch listed, people who commented on your things, people near you having art shows, contests from groups your in, features in groups you in.
Sometimes I wish we could personalize the activity feed more like Flickr. There's one photograph I commented on that now fills my feed. Every. Single. Day.