Duplicate Title Tag Problem in GWT for WordPress Blog

Hello everyone

I run a wordpress blog and when I checked my blog statistics using Google Webmaster Tools, I found that each and evry article of my blog has “Duplicate title tag” problem in “HTML Suggestions” section of GWT.

The duplicate title tags are detected for each article in following format:

https://www.example.com/its-an-example-of-problem/
https://www.example.com/its-an-example-of-problem/?comments=true
https://www.example.com/its-an-example-of-problem/?postcomment=true

As you can see, the problem is occurring because of the extra comments=true and postcomment=true parameters in URL.

Does it happen for all wordpress blogs or I have some settings enabled for my blog which should be disabled?

Any kind of help would be highly appreciated.