Technically, this is not a rock-solid proof
Apart from having an alternate account (which is not a violation of forum rules anyway), this dude might have been framed (even if it was). How do you really know that MrDongyy is actually MrFreeRoMan other than by seeing someone linking to his Facebook and Twitter accounts? Disclaimer, I'm in no way affiliated or otherwise associated with either of these forum members. Just come to think that people should be more responsible and stop witch-hunting (finding instances of plagiarism is not witch-hunting, just in case)
This user not only used the same social networks, but even the same ETH address
Okay, let's assume it is the same person
And so what, given the alt account was active 3 months ago (i.e. likely before the ban), so it is not being used for ban evasion? Is having a second account now an aggravating circumstance, I don't get it (unless account farming is involved, of course)? Or should it get banned too? The forum rules are clear that alt accounts shouldn't be used for ban evasion, but they say nothing about banning all known alt accounts of a user along with the offending account. I think banning the offending account will suffice unless other accounts are used for ban evasion (which is not the case with respect to MrDongyy). So why the witch hunt?