Looking at post history he is/was rich (?) and used some addresses
2011 address
https://web.archive.org/web/20181118133953/https://bitcointalk.org/index.php?topic=53888.msg655867
Last transaction: 2015
https://www.walletexplorer.com/wallet/1ce41055bde615a6?from_address=1tabCzGVPEK6kCJpQhFKwpXcsdnhTXyY4
2012 address
https://web.archive.org/web/20181118133957/https://bitcointalk.org/index.php?topic=76661.msg851287
Last transaction: 2014
https://www.walletexplorer.com/wallet/2e072bdb2773aaf3?from_address=1G12XfoPSLYiCdCH49qtN6NHMmHPQwPUta
2012 address
https://bitcointalksearch.org/topic/m.881225
Last transaction: 2011
https://www.walletexplorer.com/wallet/ec65b769cf53b894?from_address=14TmNWeLZNurQtmxAi62DH8RHn2pQPH2yc
He owns these wallets
https://www.walletexplorer.com/wallet/1ce41055bde615a6/addresses
https://www.walletexplorer.com/wallet/2e072bdb2773aaf3/addresses
13AV2U35JxfNBiw7tTjBUsbAtZZt32bBYH
1ABSKEnh51VSafuwEuNue9asc7X4TnU9iB
1PLGrwniHFUyXrhyQAswGJDQuKKx7D2VYF
1G12XfoPSLYiCdCH49qtN6NHMmHPQwPUta
1idL6feqziEfNvz5nZuotNeQqz39w4LN9
144c5cAfagPEURS5UT8d8oZvZuwdoKSQMw
A signed message from one of those address will prove the ownership.