Thanks for all your feedback on this issue. After much discussion we've concluded we won't be implementing this feature request. Our goal is to continue to simplify the product, by focusing on building for the majority of our customers. Whilst the ability to disable comments on a specific page or blog is a completely valid feature request, we believe it just crosses the line in terms of adding an extra level of complexity to the product and is a use case that isn't catering for the majority of our customers.
In saying this, there are several ways in which this can still be achieved. For example, David Simpson has written up a blog post of how this can be done with a simple user macro on a page. Alternatively you could write a plugin to hide the comments block on a page. We welcome the plugin developer community to tackle this problem as it won't be something we will make core to the product.
Thanks for your patience with this issue.
Confluence Product Manager
smansour at atlassian dot com