This is a good place to mention only including details that are pertinent to the story. In this case, we don't care about the content of the post, only that it's someone else's. I might rewrite this story as:

    set_up_topic("My Topic")
    create_and_sign_in_user_with_roles("user")
    navigate_to_another_users_post_in("My Topic")
    cannot_see_edit_link_for_post

This way, only the things that matter to the test are specified in the test. These things do matter more in the case above where you can edit it, though.