That's very true, i noticed that too but what are the steps the administration of the forum are putting in place to prevent these Original zombies, as you called them from taking advantage of the signature system to spam the forum.
Don't lose faith for this forum. We want the same thing, i.e., to clean this forum from spammers/bots/zombies. The administrator has taken actions for this problem, here:
129 users who were wearing a yobit signature and had at least 1 good report against them in the last 14 days are banned for 14 days. All yobit signatures are wiped. Signatures containing "yobit.net" are banned for 60 days.
Some people were talking about neg-trusting spammers for spamming. This is not appropriate; report the posts, and if that doesn't seem to be working well, come to Meta with specific examples and suggestions.
Also, these old, high-ranked accounts, are pretty much useless. Good (BTC) campaign managers always do due diligence before accepting someone to their signature campaigns.