On my humble opinion, custom CSS should be available as default.
I’ve seen enough good pages without custom CSS to say that, most of the time, it comes down to artistic skill.
Custom CSS can also be used maliciously.
How?
For example by hiding certain elements, changing/adding text, misleading people to click where they normally shouldn't, and so on.
I see. I could figure out to where all these exploits could lead.
On this case, it's better for people to stick with the standard rules for their pages creation.
