The only thing that could be done would require some extra coding such as only one of their posts per day would actually bump their thread in the sub. There's something similar in the Alt Coin Ann board as there was a similar issue of shitcoins spamming their thread to the top constantly. Maybe deleted posts in that board should be shown only to mods so it can be spotted easier. They could be expunged from mod view after x amount of days maybe a week or so). For now you'll just have to keep reporting them.