Can you stop Facebook from publishing your comments/likes to Newsfeed?

[Sarah]

Today I asked a question on a business's Facebook page about a product I'm interested in purchasing.
To my surprise a friend was able to 'like' my comment.
This friend is in no way connected to the site I was interacting with.
How can you stop this from happening?
The comment didn't show up in my own Newsfeed or my wall, so I assumed none of my friends wouldn't be able to see it either.
I had 'show in Newfeed' checked because I want to get updates from the business in my Newsfeed, but does this also mean that every one of my friends can witness all my comments to the business?.
I don't really see the point in publishing everything someone likes or comments on.
Is privacy even possible on Facebook?