As an addendum to the clause regarding deleting/modifying posts, I believe that if a thread becomes "off-topic", a moderator should list an example of what content an off-topic post might contain.
This thread is dealing with how to treat snakebite wounds, not about how many ways that Revan is teh pwnzors. Any posts containing anything not related to herpetology or first aid will be subject to modification, and perhaps a warning to the poster - PX
Okay, so that was a pretty schlocky example. But to the point, I've seen a sort flip-flopping in some threads which are "sorted" by certain staff members to "on-topic" and "off-topic". As far as I'm concerned, there should be a clear definition of what constitutes as an off-topic post, so that more off-topic-ness will be prevented, and that people won't be clueless to why his/her post was deleted.