At the very least, if I delete something, it is a signal to my peers that I “take it back” and no longer stand by it, for whatever reason. 

It seems like baseline respect of users to have it 

 Yes, tombstones are the right way to handle it, most clients (including coracle) don't have good support yet though 

 That would be nice. I posted a listing and a few relays failed so I tried again and ended up posting like 4 times. I'd like to delete unnecessary listings