I believe that, considering that the game does well in having a controlled environment and keeping the immaturity at a limit and profanity/rule-breaking is little to nothing when it comes to publicly chatting in-game; 13+ is a decent age for people to begin joining. However, rule-breaking and profanity isn't quite as controlled sometimes when group chats are active or people are in whisper/party, but that's not something to discourage members from joining the community at a young age and participating in the events during the year. FeralHeart will always be a good place to improve your roleplaying range and it's incredible to see how quickly people who are "illiterate" can quickly learn from others and become part of the "literate club". Not only this, but making friends on FeralHeart is the quickest process I've witnessed amongst my days in different gaming communities.
What I don't understand is why people are quite so "woah" if someone over 25 plays the game; it's a family/kids game indeed but just because FeralHeart is 13+ doesn't mean those older and more mature aren't welcomed. Having adults around to supervise the behaviour of our younger generations make the game much safer, and I don't believe the age requirements should go up or down. Children beneath 13? Well, their parents should be consulted nevertheless or should be limiting the access the younger children have across the internet; FeralHeart potentially being involved. Children accessing everything in the internet isn't entirely their fault, as it is the job of a parent to hold responsibility over what their kids see and hear online to prevent them from harassment or worse; so if they pick up some vile behaviour from the occasional mischief of Local in FeralHeart, that is neither our or the children's fault, but the parents for not taking more responsibility over their online safety.