I had the same request. I didn't find an existing solution, so I did it by copying from the standard Blog site template, plus custom coding.
From the template: Copy the definition for the blog comments list. Remove the lookup fields, and use a feature to create the list on all publishing sites.
Custom code: Add a feature receiver to the comments feature, and use it to add the lookup fields for page id and title, (using the pages list as destination). This needs to be done in code because you can't configure the destination list for lookup fields in XML, (or at least I don't know how).
Write controls for querying the comments list and adding to it, and place on the page layout.
Simpler approach: Don't use the standard blog comments list, just create your own, where the page reference is just a number and not a lookup field. Pro: Less work. Con: You miss out on the views that come with the standard list.