Using the same username on different platforms only comes with a transfer of reputation and trust advantage if the user can fully prove theyre the same person. I wouldnt trust someone with Theymos as a username on a different platform. Therell have to be need to verify which makes no difference in general.
I posted about this days back.
It doesnt make much sense trusting someone on the internet just because they seem to be familiar. Thats an easy scam, Newbies fall for. Accounts get hacked, sold, and people change. Always take precautions and cut down the risks to the minimum.