Let's face it, we shouldn't need to underline that we should all act with consideration towards others, just as society shouldn't need to codify respect towards the elderly. But it is the world we live in now.
Well OK, include something in the Code about treating other visitors with respect if the tone of the times demands it but also do make sure it talks about treating the feelings and sensitivities of others towards the site with respect. Without that, you'll get people climbing on stones because THEY think they can justify it and bidding a cheery hello to annoyed or affronted spectators and thereby claiming they've kept to the code. Codes have to be cute else those that simply want to do their own thing will interpret them in their own favour.
(PS I have a lot of experience of studying the effect of badly drafted codes of behaviour and how they can act as cloaks to facilitate bad behaviour. Every detectorist bar none swears they adhere to the Code For Responsible Detecting and tells every farmer they do in order to gain access to the fields yet it's statistically demonstrable most of them flout it. That's an example of a well meaning but badly drafted code having the opposite effect to what was intended. We'd be far better off without it.)