The reasons I do not know. But I think that due to the fact that 2 of my old messages were deleted in one day.
With such a message in personal messages
There is no correlation between deleted posts an banned.
There are three main reasons for banned profiles as far as I know;
Pliagarism
Posting malware
And ban evasion. You have to have broken one of these rules, also a newbie account can be nuked if it repeatedly breaking forum rules as soon as it's registered.
And from the above reports, you are guilty of pliagarism.