Now, when you subscribe to a YouTube channel, Google notify you to "all videos uploaded, rated, favorited, and commented on" by a certain YouTube user. To change this default option, click on "edit subscription", selecting "Only videos uploaded by ..." and "Default to this for all future subscriptions". YouTube's options page lets you disable your activity feed. "If you'd like to change which of your actions’re publicly available on your channel and Recent Activity Feed you'll need to make updates on Sharing Settings page. There, you'll see many actions, and boxes next to these actions. Selecting a box, appear on your channel, and users subscribed to you’ll be notified when you perform this action."