Nothing unusual. Check his registration date, seems that all the posts were deleted and that's why the activity went 0 but the merits are there. I guess it's a tradet account and the buyer is covering tracks by deleting old posts of the previous owner.
I don't think this is the case, actually. I don't see a single "received merit" when I check under their history. It seems that it was just a "bug" during the initial distribution of merit. When the system was released there were certain members that had their merit counts incorrect. It's possible that they just received an incorrect amount of merit to begin with. Deleting posts that have been merited does not cover up your tracks, it just keeps the merit stats and replaces it with "Deleted post" +1 or something. Do you have any proof this person has received a single merit?