Again, if you don’t use said vessels (eBay, Reverb, PayPal non gift) you have the complete FREEDOM to sell to whomever you wish, on forums/Craigslist/FB or word of mouth. If you are using a business that makes a profit, that they have to report to the government then you will be subject to taxes unfortunately. We were lucky for over 20 years in not having to deal with that on the net.
What you are suggesting is only possible by using these businesses to sell our gear. Beyond that, the government would have to audit everyone’s personal property, year in/year out, and at the same time our bank accounts to determine if we sold any property at all that they could try to tax us with.
Doubtful to say the least.