I haven't seen any porn here either, but 10 minutes in the FAQ and the terms of service didn't find me anything involving porn or sex or adult stuff, so it could show up some time.
If it does, you should definitely check out Hubski's filtering features in detail. This place gives you tools to moderate the entire site just for yourself. You can filter (aka block) specific people, tags, and domain names. You can also mute specific people, which prevents them from commenting on your posts (and possibly your comments? not sure).