Sitting on another user is not considered an issue.
However, inappropriate subjects in the chats along with how one might do this or the usual, sudden buttswing on top of someone is well enough. As mentioned above, if you leave your character afk for 10 minutes you are indeed putting yourself up for some risks.
To be very honest, there's so many ways users try to come up with excuses or find holes to get away with a ban placed due to their inappropriate behavior, even though misjudgement can happen it's rare. The excuses for getting caught are many. But plainly sitting on someone not saying or doing anything else is not really a ban-able offense unless as mentioned, there's more too it.
This rule overall is nothing hard to follow.