So if they get hacked! how they wanna restore their account ? because hacker see they signature on this topic
You need to have control of the private key of the BTC address to generate the signature, that is how admin will know that you have control of the bitcointalk username because you able to sign a message with the BTC address you mention on your profile signature and it is verifiable from your posting here mentioning you have control of the BTC address , mathematically it is almost impossible to find the private key from the signature
This is Yury1 from bitcointalk.org and today is 2018/03/23
BEGIN BITCOIN SIGNATURE
1QG1zoEui8qsBaSTA1fh6UgNdJAaBTHs15
-----BEGIN SIGNATURE-------
IEM6xWPLA8O8PLF7dtcxqLHywmRHIiWbPdhSKELvKpvmOjeDQoftTMmPpsDO1NiVBRedvJkx2Jrlwh8 bHhwF+Xg=
------END BITCOIN SIGNED MESSAGE--------
Quoted and verified
BEGIN BITCOIN SIGNED MESSAGE-------
Hi, I am Istklin from Bitkointalk.org and today is 2018/03/23
BEGIN BITCOIN SIGNATURE
1EtawwuvDJmxgzAMkCkqSnxVBMbntJ66x
-----BEGIN SIGNATURE-------
H43swGjFqur9q2Z3HjlpvanwxtPkOdgJIYvJYQdBtFXyJ9eKEKViMeHW9j8LoD3fByZxHh2vzfmX3CT/JZwWITI=
------END BITCOIN SIGNED MESSAGE--------