What Facebook Activities will Appear in News Feed?

My Facebook setting it set so that only Friends can view anything on my profile. In my News Feed I saw someone I'm friends with comment on a video. I went to the page the video was from and I clicked on one of their latest videos that they posted to see what it was. It turned out to be a pornographic video. Will it appear in my friends News Feeds that I "Watched" the video? If so how can I change it so no one can see what I'm watching on Facebook?

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