What part of this isn't clear?
"Rule 5 isn't really a rule per se, as it it's not something that posters are either to do, or are not to do."
The first four points are part of your code of conduct, what is expected of you when you travel TFL. Those are your RULES for participation.
The fifth is not rule because it gives you no definitive guidance. It indicates only that the staff is the final arbiter. At best, it's a notice.
But, since you seem to be quite worried that somehow the staff is going become zealots tomorrow (I can tell you definitively, that's not scheduled until March), I invite you to write a set of rules that covers ALL possibilities and eventualities of what might transpire on this board so as to guide staff and to ensure a fair and equitable application of the rules in all circumstances.
Simply stating "one will not insult other members" is not enough. To prevent the boards demise into heavy-handed zealotry, you must give every possible example of what constitutes an insult. You must also include a comprehensive list of when an apparent insult is not actually an insult.
Another problem area in the past has been the occasional advocacy of illegal activities by some on TFL.
To prevent this in the future, we need a comprehensive list of all illegal activities, all potentially illegal activities, and it must be broken out to the Federal, State, and Local levels given that what may be illegal in one state may not be necessarily illegal in another state.
Of course, that's just the tip of the iceberg, a few examples to get you started. I'm sure the comprehensive list of rules will be far more expansive than that. In fact, I know it will be.
I figure this shouldn't take you more than, oh, say, a few hundred years if you really put your shoulder to the wheel...
See how ludicrous it is to try to craft a comprehensive set of rules for a venue such as this?
TFL's four rules and one guideline have been in place now, without too many changes, for close to a decade, or a bit over.
I've been a member here since 2000, and many of the same names continue to occupy staff roles.
Given that they haven't revolted, seized control, and imposed their own brand of zealotry on the boards should tell you something.
It tells me that the four rules and a guideline work, and to put too much effort into worrying about their application is time wasted that would be better spent doing something more productive.