On Facebook, how to prevent my posts and comments on others' pages from being in my friends' newsfeeds?

[Louise]

I posted on a facebook page I like (but am not a facebook friend with the person), other people responded and we had a conversation by commenting on my original post. This is not showing on my Facebook timeline, but one of my facebook friends has informed me the conversation is showing in his newsfeed! Which Facebook settings will make sure such conversations are only viewable by people visiting the Facebook page I post on? Our whole group of aquaintances will welcome advice to resolve this!
The facebook help section says the following: "Your posts that are not on your own timeline:
You will not be able to use the audience selector unless you are posting on your own timeline. If you post to another person's timeline, the person whose timeline you are posting to controls what audience can view the post. Similarly, when you post on a Page or another public space on Facebook, the post will be public."

This still doesn't explain why usually when I post on someone else's page (also not a 'friend') it doesn't show in my friends' newsfeeds, yet on this person's page today, everything I post is showing in their newsfeeds (not my timeline!)
Thanks abraXus, but Facebook help says adding someone to your restricted list can only prevent them from seeing ehat you post on your own timeline, not what you post on other peoples' timelines (public).

[abraXus]

the only way is to add people to your restricted list