...If you create multiple account and use same ETH or any other social media including email, you will not get red tag if you do not join on same bounty/signature campaign. But you are not allow to exchange merit between alt account.
I haven't created multiple accounts. I started to award Crypto mania posts when they were a better quality not from the start. It took a few months before I sent the first merit to him.
I have even asked Crypto mania to not merit my posts at over a year ago when there was a lot of accusations and red paint for merit abuse on the forum.
I can't find my PM but this is the answer I got from Crypto mania back then.

Later there was a post from Theymos on the forum that there is no red paint for merits so I stopped to be worried about and merited further all good posts.
Do you think I will be so clever and write almost a year ago PM's about merits to myself and not take care of the same ETH addresses and ref links if this was my alt account?