My point is does a spammer many years ago will forever be spammer and won't be able to improve his posting quallity?
No. Of course they can improve. There's many examples of this over the years. It's quite typical that new users don't really care too much, and then change their mind as the forum grows on them, almost becoming a sort of second home to a lot of users here.
People in general deserve second chances. People develop over time, and typically learn from their mistakes. However, this varies from user to user, and I imagine most signature campaign managers would take this case by case instead of automatically ruling out users based on their past posting habits.
So, don't give up. Continue to improve, and if you contribute significantly to the forum, more than the noise you may have created before. People will notice, and generally be willing to forgive and move on.
actmyname hasn't been active in a while though,so getting the trust removed might be difficult. However, this is another point other users should take into consideration when evaluating a user.