There are several players that fall into this category. Some discovered it by accident and others have exploited a problem with the shiplist.
Carriers have the BPV of their fighters added to the BPV of the ship. This can make even a light cruiser have a BPV in excess of a Dreadnought. The replacement ship for loosing said light cruiser is based upon BPV, however. So, a 3000 pp light cruiser becomes a 18,000 hvy battlecruiser when its lost. Conversely, if you loose you're 18,000 pp battlecruiser, you might be given a carrier as a replacement, eg a fighter carrying War Destroyer thats worth nothing... (I know, it hapenned to me..) This was something not anticipated when the fighter BPV's were added to the ship BPV, so the replacement values for ship, especially carriers are way off. Sadly, some (not all though) have exploited this. The tell tale sign is of course a very low glicko, and a huge amount of accumulated prestige far in excess of their lifetime prestige.
Now, many players have had this forced upon them, by loosing ships unintentionally. Something I've said before and will say again though, one thing about 'testing' for bugs on a server is that players will always find any loophole you may have inadvertantly created and use it to their advantage... lol!! Makes for server testing though... he he.
Several players have sent Herr Burt emails actually stating that their accounts have become larger as a result of trading in ships that were replacements for lost ships, and have asked to have their accounts edited. By and large, most players have been honourable about it, nevertheless, DOE being such a short server (and almost done now), editing player accounts (I'll speak for Herr Burt here) probably wasnt worth it.
To the best of my knowledge, there were no CnC rules for DOE, so players could fly what they like.