veeren till he got dismissed, but 13 is reasonable to let him on if you think he can handle it. and you say he knows a lot about sports so as long as he knows what he is talking about i say let him at it
you could like watch what he posts on and about and stuff to make sure he is on topic and what not, but it is atleast worth a try. I know how much i loved UT when i was 5 much less 13 and now 18 and i would have wanted on.
only problem is i only found out about this about a year ago.. (sad, i know)