The accounts signed in chrome browser can be used through a Opera browser. The accounts means Facebook,Gmail. For example, I can open a Gmail account which is signed in Chrome from an Opera browser without entering login information there. Also if i logout an account from the opera browser it reflects in the chrome too, means the same account would be signed out automatically from Chrome. 
  I think the issue would be the both browsers might be sharing the same sessional details including the login information etc.
  So, the both browsers Chrome and Opera cannot be used parallally in a same computer as the account change made in opera affects the Chrome. 
  You can verify the bug by installing the two versions of the browsers and OS i specified.
  Sir/Madam, I request you a sudden action on my report.

Thank you
  
VERSION
Chrome Version: 50.0.2661.102 m ,the latest product from google
Opera Version : 37.0.2178.43 stable
Operating System: Windows 8.1 Pro