On Magento ver. 188.8.131.52 using the default checkout, when a user selects to pay via PayPal step 6 (Order Review) is being skipping, but this step is essential to me as it has order comments. How can I make sure the user sees this step when selecting to pay via paypal?
By design the user leaves the site for PayPal Express after step 5. They return to a separate order confirmation page. You would need to add your comments module to that final page (/paypal/express/review).
Alternatively you can use the old style PayPal Payments Standard where the user completed order at step 6 and then proceeds to pay. I think this method is being deprecated though.