There is a post on the CS forums that the moderator there confirmed that alt posting very rarely happens as they’ve confirmed them-self. To answer your question; no it’s not happening.
I can’t really agree with you on this because of the proof that the forum moderator gave in this thread: How to report a forum troll
Scroll down to post # 21 from [Vrakthris]. That’s all the proof we need to confirm that alt accounts aren’t a problem.