Coming from a PC software background, I would guess the character deletion is probably done to increase efficiency. Let us postulate the following about account hackers and their methods:
Efficiency is king.
The more accounts they can hack and process into adbots or gold-accumulation bots the better.
A person is much slower than a software-automated process.
Software automation for fixed GUI elements is easy. Software automation for randomized GUI elements is much harder.
Presuming that, it follows that they would write their post-hack account processing software so it does a few things:
Find all current characters in your character list on your most populated 10 servers (the game automagically sorts the server list so they show the ones where you have the most toons)
Log into the level 80s, disenchant or sell all BoP stuff or worthless BoE stuff to the nearest vendor and send any resulting gold to a designated level 1 "clearinghouse" alt for that server.
Repeat for the level 80's guild if they have access.
Rinse and repeat for all other characters on those top 3-10 realms. Hell, might only need to do the top realm as most people only play on one realm. (Remember: efficiency is king.)
Delete the char from slot X (whichever the processing software is set to use for its advertising/transferring) on every realm where a char exists in that slot.
Create level 1s with random gibberish names in slot X.
Advertise or transfer gold/gear/etc. on the level 1s on as many servers as possible.
I'd presume that's the basic method for generating the most "work" from a hacked account as possible within the short time period they usually last before getting banned.
You may be right, a lot of the gold spammers lately have been <charactername>wsjdka, which could be software tagging a level 80, stripping it, then erasing it and creating a spammer character.
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