How about a e-commerce site in the Fediverse where you can either sell second hand stuff (like ebay) or sell stuff you made or paid people make (like amazon or etsy) but with multiple instances with different moderation, shipment costs and some might require you to have id obviously their will be sketchy instances or users but the community could make a list of instances/users to avoid or to be careful of at least, and most the users on this list would be user who their instance hasn’t banned (which might put the instance into disrepute, since if they are notorious enough to land on this list you should probably ban them) and the people who are in charge of this list can get reports from user and they will have to conform from other buyers who bought from that individual to make sure people aren’t lying because they don’t like the person or something, it could be federated/integrated with services like mastodon, peertube and possibly lemmy where you can sign in with it with your account from these services, but you have to make an account with this service to actually sell anything, but user from these other platforms could link their shop on this service on their mastodon post and/or account and peertube videos/account (sorry if I got carried away), what do you guys think?
Doing something like this “for real” on any scale takes a ton of anti-spam and anti-fraud effort. Look at how big a pain it has become to post on Craigslist, which doesn’t even do commerce directly.
On a small scale it’s less of a big deal. If you want an actual sales and payments platform like Etsy, it would have to be done by an organization of comparable scope, even if offloading payments to Stripe or whatever. Lots of seller vetting, dispute resolution, etc. I don’t think it’s impossible but it’s not just a matter of software. It would need paid staff dealing with hassles all day, imho.