this is a post from 2014, is it still valid? My guess is these admins get thousands of pms per day no? besides, I don't have access to private keys I owned back when I created the account...
You are likely out of luck then. The thread is still valid, and was last edited on October 25, 2017.
I'm sure they get plenty of PMs but this is the only officially accepted way to recover an account on this forum, and having a signed message from a known address is the #1 form of proof. I've seen, in rare cases, other examples of proof be accepted, but generally speaking you have to have a signed message with an address you've used in the past and can be verified. If you do not have any of the keys back then, you are facing a very large uphill battle recovering and proving it is your account, and this battle is one that many have failed at.