I actually think his posts got deleted with the recent post recount made by theymos when he deleted thousands of posts and threads and a lot of people were complaining about having less posts or as you said he deleted them himself but it wouldn't really make much sense.
Well I was not aware of this, so I guess maybe this is case here, because I see posts back from 2014 so maybe you are right. I've seen before newbies with 100 merit, deleting the history to remove any evidence of possible trading. Of course when you see an account registered back then with no activity and full merit then it is suspicious.
It's easy to spot a purchased account. If you look at the post history and you see perfect English and quite some knowledge and then a pause for 1 -2 years and suddenly, the guy started posting only in the Russian local section for example, asking how to find his profile link or just a newbie questions, you know, then it is obvious that this account doesn't belong the the original owner anymore.