False.
In reality is it the other way around.
You might not have understood what I meant.
The Bitcoin address or public PGP key cannot be use to impose another person.
Most user have this information public available in their signature, contact information, keybase.io etc.
There are increased scam attempt where people tell I can't sign a message because I am using 'Wallet X' which doesn't support signing. If user(1) know what type of wallet the user(2) is using, for example Coinbase, he(1) can put that address here which make others think it is alt of other account(2).
But you need it to published somewhere in bitcoin talk in order to be able to retrieve your account if it gets stolen.
That's why I also suggested to post PGP key and the link to PGP pub key hosted site will be helpful if he his PGP key has changed.

Publishing a generic signed message is not cleaver, it can be used by an imposter.
If you sign something, the message must include the purpose of the signed message and include the time/date.
This is an example of a not so cleaver signed message:
Message: "This is TookDk from Bitcointalk"
Signature:
This is much better:
Message: "Date: 2015.03.19. The purpose of this message is to prove that TookDk from Bitcointalk is in control of bitcoin address 1TookDkVTaqsCn56Xo7aMfUMAUN3NhRjN at this point in time"
Signature:
I understand and I never recommed a person to do that. Even if one posted here, it is hard to know whether he signed it the day he posted. IMHO if signed message can include date and time automatically, it would be far better. It can also be faked by changing the date and time in your computer but I don't think an owner signing will do it when posting important things like this.