The only way through which you can check the account ban is by checking post quality.
If post quality is good then the chance of previous ban are almost none otherwise you know what I mean.
there are other reasons for being banned other than spam(like PM spam, spread malware, flame wars, excessive pumping in the market place, among others).
And the spam posts might have been deleted too by mods.
So there is no warranty about whether an account has been banned before or not, even if the posts are OK.