The PM contained enough information for me to believe the account has changed hands one way or the other, and certainly the numerous posts that got edited around October of 2017 shows someone went back and changed all of the addresses.
The address you gave wasn't posted that long ago so I personally would find it hard to accept as proof that you are the original owner, but at least the owner as of September 2017. Regardless, I certainly would not recommend anyone trusting the gallery2000 account at this point.
And, if you want an older post to work on a bitcoin-based signed message:
https://web.archive.org/web/20150519081241/https://bitcointalk.org/index.php?topic=627899.0
The original was edited to change the address but the unedited version from 2014 in the link above shows that you sent 1 BTC to:
17wPsP8H8eZttqRRzuuwWbCU2xLYrkCeWV on May 26th, 2014
Which came from 1HcMZzwrriBmipDi224npxnix4SHU7BXNZ
https://blockchain.info/tx/370ffb70f1a4551d363cb9748ba367e3711d15f97de16de4317c0e6dadb32a48
Can you sign a message from this BTC address? 1HcMZzwrriBmipDi224npxnix4SHU7BXNZ
I think that 1HcMZzwrriBmipDi224npxnix4SHU7BXNZ is with localbitcoins.com where I used to mined and sold.
From the https://web.archive.org/web/20150519081241/https://bitcointalk.org/index.php?topic=627899.0 , it shows my website http://www.slimdiary.com was in my signature. If I can prove that I own slimdiary.com , would that prove I am the owner of gallery200 back in May 27 2014 also?
Also, if you check my IPs address when I posted in 2014, The IPs would show that I was in Florida which matched with my IP address now.