This is part I of the FAQ, which is about the care and feeding of the mailing list and its denizens. Sex, and things related to sex. Sex is by definition on-topic.
Related topics are usually on-topic.
Hopefully they don't mutate further. Personal attacks are almost always off topic. The list manager tries to maintain a hands-off policy as much as possible, but if the thread goes on too long, he generally steps in and asks for it to stop. ObSex means an OB ligatory SEX ual reference. If you just have to post something off-topic, you should include something sexual at the bottom.