Only him? Nobody else?
I cannot say for sure if it was an authorised signature by Wasabi or not but what is going on? First it was Unnamed Exchange that copied the Yobit banner of all banners and now this....
Wasabi is not a profitable service, and therefore has no signature campaign and therefore I doubt: 1) It is authorized - but you do not need anybody's approval to promote their activities with your signature. 2) It is authorized to plagiarize the signature.
If it is only Gyrsur, I
suggest that you contact him and get this remedied. I have sent him a PM.