"Just keep in mind that by making this, you prove that PC users are still closed minded bigots who don't recognize a good thing when
they see it." This is making fun of the Mac commercials, not the Mac...you just proved that Mac users are pretentious hippie *ssholes.
Oh, and I forgot, your change of "(mostly)" is incorrect, too. You should have moved "mostly" after "have". So the moral of this story is that you shouldn't post grammar corrections unless your own grammar is impeccable.
"15-year-old" is correct -- though in prose it should actually be written "fifteen-year-old". Also, both the "and that" that you corrected and your resulting correction to "which" are incorrect; you should simply have added a comma before "and".
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