13 is the age of entry for a lot of social media and I think this place is probably safer than the comments on YouTube for example which contain some hateful and mature stuff.
I appreciate you considering this though, maybe brough up more because of the bad blood you have seen around the place, especially Craig etc but I still think in the grand scheme of things, this is a more productive and creative space to let a 13 year old than Facebook or Twitter for example.