Speaking as a frequent reddit user where various subreddits have added their versions of such an instruction, I think I've never really been reminded by them to

Speaking as a frequent reddit user where various subreddits have added their versions of such an instruction, I think I've never really been reminded by them to behave a certain way. Parts of the UI like that can really only be seen once: once the user has seen that it is just a warning that is always there, it becomes an uninteresting piece of clutter that is zoned over and never again influencing the user. I think the current system works much better: a thoughtful and appropriate comment written by a human when deemed appropriate (or possibly copied, I don't know). This reinforces the ideas when necessary, and by itself is already a push for humanity, while a robotic repeating reminder serves only rarely to reinforce good reactions.