Wow, what a headache! I've been doing a ton of research and trying to get my taxes in order for 2020, and just learned about California's Marketplace Facilitator Act.
To keep it short, SS is not legally compliant as far as any sales made by customers in California or to California-based sellers, because SS is not collecting and remitting sales tax per California state law. (More info here: https://cdtfa.ca.gov/industry/MPFAct.htm)
There might be other states with similar requirements, but with California being the largest economy in the US, it seems like a pretty big issue to ignore. All of the other sites I sell through are in compliance and collect and remit sales tax properly: Etsy, Big Cartel, Shopify...
I don't know if anything will come of my email (hopefully it will), but it seems like I'll have to move my shop to another site to avoid the legal vulnerability.
I also just saw that SS privately filed for stock market listing this week...Seems like you'd want to get all of your taxes and legal obligations in order first, no?