This is the answer.
Matrix needs to make it easier to expire or delete messages from the server, but other than that it's doing a lot of the stuff Signal should've been doing years ago. Easy to use multiple devices, easy to get messages on multiple devices, keep chat history in sync, no reliance on phone numbers for identity or single identity servers, good working federation / ability to set up private hosted groups, etc.
Yes exactly. No online platform can catch 100% of prohibited activity. They are punishing the wrong people. What they should do is get a list of all the ones eBay missed, file charges against the seller and start knocking on buyer's doors. Or maybe send some agents in an undercover Prius to pull them over and issue a fine when they get coal rolled. That would send a pretty clear message that eBay is not a safe place to purchase these items.