Wrote an e-mail to Cyrus, but I no longer have any of my old bitcoin wallets. The only proof I've got is a post with my e-mail address (The one I registered my account with).
I'm afraid your e-mail address cannot be used to prove ownership. What is required is a signed message like it is explained in this post:
https://bitcointalksearch.org/topic/recovering-hacked-accounts-or-accounts-with-lost-passwords-497545
Even then, you would have to wait, and the chances of your account being restored promptly are not so good.
Once I found out, I clicked a link to lock account and I can see that there are no new posts from that moment.
That's pretty much all you can do right now to lock the account so no more damage is produced.
Why do people want to use some old unused for years account?
I suspect the reason is your merit count (10) and higher rank (member). With that, they can participate in bounties and earn some rewards.