Well they can't unless there are no other groupthink comments present. By definition a controversial comment isn't getting upvotes from a significant portion of the group so any regular "good" comment will quickly push it down to the bottom.
If the majority of your group is rational, a rational comment will not be controversial even if the view is unpopular. However, the vast majority of the population is not rational when it comes to reading unpopular opinions and that shows in every subreddit.
If the majority of your group is rational, a rational comment will not be controversial even if the view is unpopular. However, the vast majority of the population is not rational when it comes to reading unpopular opinions and that shows in every subreddit.