Well, it wouldn’t make people buy a gig they don’t really want to buy most probably, but it might make some people choose the gig over other gigs they are contemplating if the displayed badge was for a course that the potential buyer thinks is relevant, and the other gigs don’t have that badge.
IMO, “No it wouldn’t” is just as unfounded as “would increase”, “could” is much better, and “might, in some cases”, is probably correct.
The only problem I see with the suggestion is that the gig page might become too cluttered, between the actual gig description that most of us want our buyers to actually read, the recommendations of other gigs, and whatever else there is already.
To me, the most important thing on my gig page would be a presentation that makes buyers read my description, but it wouldn’t hurt if the badges were displayed somewhere below that. It might increase chances of selling the gig, and it certainly wouldn’t decrease them.
In any case, I fail to see how this suggestion means that someone isn’t doing other, (I’d agree) more effective things like researching their competition, too, and it certainly doesn’t indicate that their gigs, or they, are superfluous.