Sure it can, but having one would definitely decrease the level of freedom of speech here. And I'm very sure that people who have a problem with JT having no such code would then argue over different interpretation of that code. Countries have laws, but then they also have courts and lawyers. If JT had a code of conduct, the moderators would be the ones who have the final word on which interpretation is the right one => the situation would be exactly the same.

Moderators are the only ones who can edit or delete some elses posts = they are members with special powers. Which I think is quite obvious and I don't think it has to be written down somewhere.