Hi, Buyer here.
I found a seller (voice-overs), we agreed a price and I admit to being surprised to be asked to tip. As a professional, I think you specify what you want as clearly as possible, agree a price and pay it. The seller was great and I've placed two more orders.
Then Fiverr came back with a survey asking if I was happy with the seller. I said yes, they were great. Up pops a big message saying a "20% tip is Normal".
No it's not and I find the whole approach annoying. I will continue with fiverr for now because I found a great seller and want to finish a series of videos. I will not come back again.