To be straightforward, I don't think there is a need for a definition of what is dishonesty in the audio world.
But, to play along for now ...
Rather than an exclusion for reviewers, I see this differently. I understand the recognized audio media to be an industry participant. They are recognized as such by the manufacturers, distributors and dealers (but mostly the first two) who send them equipment to write about. Industry level events such as trade shows allow recognized media to cover the event. That means publishers, columnists and reviewers are industry members and they accrue the same privledges as other industry members. Thus their is no need to set them apart and carve out exclusions for them.
So the boundary question is who is the recognized audio media? I think the answer is is pretty straightforward when thought in terms of publications. Publications are owned by publishers who have an established staff and a set of guidelines, rules and practices for delivering accurate and vetted audio information to their readers. The staff includes editors and writers. Editors (and sometimes publishers) are the gatekeepers for the guidelines, rules and practices and act in what they believe are the best interests of the industry. Writers receive approval in advance for the topics and components about which they write and their written product is reviewed by someone other than themselves before publication.
The lines are formal and anyone else is ruled out. One is not an industry member simply by declaring oneself an industry member.
I believe any industry participant/member should, in a straightforward way, identify themselves and their role as such on audio social media and the platform should require that. And it should be relatively easy for say, WBF administrators, to validate that identification.
A 'shill' is someone who pretends to be something/someone other than who they are or who fails to reveal who they are. The distinquishing mark of a shill is concealment. For example, someone who is a brand ambassador who pretends to be 'only' a regular customer. Or someone who receives discounted audio gear for promoting it on forums without revealing such is concealing what they are doing from other participants -- the so-called 'influencer'. This seems to be your target. Consultants who claim to sell or give away advice may or may not be shills but they are probably not industry participants.