Paid, Permanent, and Plus accounts: Custom comment pages match your journal's theme by default. You can either modify those custom comment pages further, or switch to comment pages in your site scheme by setting the option "Disable customized comment pages" to Yes, in the Presentation section of the Customize Journal Style page.
Early Adopter and Basic accounts (or any account using the old style system): Comment pages always display in your site scheme.
Maybe it's just me, but I find this part difficult to grasp, esp. for new people. After reading it a few times I now believe it's because the info about the Early Adopter and Basic accounts only says "comment pages always display in your site scheme" which is basically what the first sentence said about the default for all accounts already. For Paid, Permanent and Plus accounts there is a detailed explanation about customization. For the other accounts there should be a note that this isn't possible for them. Especially for new users with Basic Accounts who don't quite understand the difference between style/journal theme and site scheme this may sound as if the comment pages should match their style as well. My suggestion would be to switch the parts of the different accounts and start with Early Adopter and Basic, saying that the comments for them appear in their site scheme (e. g. Horizon), not in their journal style.
Underneath, the customization features of the other accounts could be mentioned.
Again, it's probably just me and last time I read it I was tired. But even now it took some time until the difference really sank in, so this small change may help other people as well.