There have been a few other --mostly unity-- packages being promoted by their creators but very sporadically.
While I am the latest “offender” that posted his own marketplace content, I’ll be the first to say that I am not too fond of people spamming their paid work, but that might also stem from the fact that I am an admin on many facebook groups and even some discord groups and have seen a looooot of “check out my pack” posts. So I do agree that some good rules need to be set in place.
Quality is always a hard thing, if a somewhat beginner is really proud of his first marketplace/gumroad package it might come across as harsh and uninviting if we delete the post because of its lower overall quality. though on the other hand, if you sell something you should also be able to take a punch since it helps improving yourself and the package in question/any new packages that person releases.
Otherwise I could suggest one specific thread where people can promote their work or work from others that they consider valuable but those threads often get ignored over time.
While I am not against ad-space, as a small solo-dev who focuses on marketplace packages even 50 bucks would result in me never using it. But it might help that I know where to post and how to reach people.
Its probably the same with job postings, while its really cheap --especially with the talent thats active here-- its not something i’d consider doing. then again, anybody who asks me if I know someone for a specific set of vfx skills I direct to this page and its job board.
I’m sure you’ll figure something out