The YouTube video shows two women, dressed in suits and ties. They smile; they sniffle back tears; they gaze into each other’s eyes. They are reading their wedding vows to one another. The four-minute video titled “Her Vows” contains no nudity, violence or swearing. There’s no revealing clothing. No one is engaging in activities that have a “high risk of injury or death.” And yet, YouTube had deemed the video unsuitable for people under 18. YouTube acknowledged Monday that it might have made a mistake, saying in a tweet, “Some videos have been incorrectly labeled and that’s not right. We’re...