Undoubtedly beneficial. In some cases, it's even preferable to reject a potential order - even if the buyer is willing to buy, but it doesn't fit their needs. It is preferable to be truthful than to suggest and insist on satisfaction.
Fiverr's forums are not for advertising. Instead, you can advertise your services on social media. It's also important to understand the basics like when and how to share your information I hope that was clear. Thank You....