Yobit had a long run signature campaign earlier in 2016 to 2017 for more than a year (don't know if it really stopped as I frequently see some users wearing the signature) with the highest pay-rate (compared to actual running BTC campaigns considering also the BTC price at that time.
I don't remember reading any complaints about that campaign. Yobit had been greatly promoted via that campaign, which may be seen as a major success factor for the platform.
For the New launched campaign, I really have some doubts about it for the following reasons:

• How long will it run?
• Why there is no Bitcointalk manager to respond different community asks?
• How much fund reserved for the campaign?
• Are funds escrowed by any trusted third-part?
• Should we blindly trust Yobit after the last accusations against it?
• How many users will be accepted in this campaign?
• Isn't weird not to set more post restrictions for a high rate campaign?

I think the issue with this campaign is a little bit bigger than the spam-encouragement problem.
We can't blame/judge participants or managers until someone break forum rules.
Reminder, confirmed spammers will be banned, so I think applicants will take more attention doing their tasks.

This is just a personal attitude, and am not accusing Yobit or participants being part of any scam/spam theme.