Kids are smart. Horny teenagers even more so. They will find loopholes or ways to circumvent these kind of things - speaking from experience. At age 13 I installed a keylogger on my PC to get the password for a parental control software my parents installed. Roughly one year later I also exploited a vulnerability in iOS 4 that allowed me to see the parental controls password in plaintext so I could re-enable Safari.
Enabling “show content for collapsed comments” helps as only the child comments will collapse upon tapping.