> A huge indication that a comment comes from the channel author.

This pattern requires that users have done something to have seen this before. While many users will see it, the users that are probably falling for this problem probably will not have seen this "huge indication" before, so wouldn't know it exists.

e.g. a user who never checks comments really, but then checks comments one day and sees the scammer might not realize there would be an indicator if it was the video's author.