New users, especially people new to discord as a whole don't seem to be aware of the pins as a whole, unless directly informed, which can lead to them taking a flawed approach or falling into some pitfalls.
It could be useful to have something on the server guide, when you join the server that has a helpful tip to check the pins of your channels of interest, which might help stop more users falling into really common, unexplained pitfalls.
I understand adding it to the rules makes it seem punishable for not doing so, but I want to be clear that, that is not the idea with my suggestion, rather, it is the first page you see when joining, so a little tip subheading may be appropriate