WordPress 2.7 brought out some great new features, a major one being comment pagination, which basically breaks all comments into multiple comment pages so that they are more organized, easier to read and lead to faster loading of pages when there are thousands of comments out there.
When I checked my Google Webmaster tools today, it notified me of hundreds of duplicate title tags and duplicate meta descriptions pages on our site which were not there before. A quick look at this duplicate content issue revealed it was caused by multiple comment pages.
As you see most of these pages had comment-page-1 type links. But our wordpress theme did NOT support comment pagination, so we had not actively enabled this feature. But a look at the WordPress Admin > Discussion area revealed the feature was checked by default.
I checked other blogs also which I had upgraded to WordPress 2.7, and all had the same duplicate page issue. The problem was that this very useful feature was checked by default. The basis was that if your theme was compatible with WordPress 2.7 (like QuickPress), it would start working automatically, however, if your theme did not support the feature, it did not make a difference.
You might be having the same issue, if your theme does not support comment pages, and if you have not made a voluntary effort to upgrade your theme – Simply uncheck the box and you are done. The duplicate pages will go away easily. Duplicate content pages is a major search engine optimization (SEO ) problem and its best to fix it early. I hope WordPress unchecks the box in the next release.