This doesn't say anything about how to remove activities such as "Economica commented on X's status" from my friends' news feeds, though. Judging from Elaur's friend's experience with deleting the 'single' update and still having it show up in friends' news feeds, I'm guessing I would have to delete the actual comments to prevent them from showing up.
But, your friends (and the general public) might be able to read your comment if they can read what's on the friend's wall you posted it on, and that's controlled by the privacy settings of the friend on whose wall you posted. I think you can only control the visibility of your comment on their wall by deleting the comment, which is why I posted the description of how to do that.
Edit: Sorry about not being very clear about this the first time.
When you delete your comments, they are gone. From anywhere on Facebook (I did this test with a friend of mine who had the same question you are posting here)
But, itīs always better to "think before you comment". Or, to organize your friends into "lists" to be sure who sees what of your FB stuff. For example, I have a list called "Work" who canīt see my pictures and videos. You can do the same if you donīt want a certain somebody to check all of your actvity.
"An intelligent hell would be better than a stupid paradise."