I don't want to get pedantic, but to get things just correct: it's true that the activate button is a way to get the users account from author to pubish, and if that is your goal, that button is the easiest way to achieve that. However the statement that users/groups shouldn't be created on publish ...

Hi Mahesh,Thanks for reporting this. We're trying to figure out how this could happen. A quick question: by any chance, were you installing multiple packages at the same time?ThanksLaurie

As of 6.1, social communities makes use of a common store instead of replicating UGC. Please see https://docs.adobe.com/docs/en/aem/6-1/administer/communities/srp.html and let us know if you have any more specific questions.