> You use the same system to handle RTBF, and if you can't, then maybe a platform where it's literally impossible to delete something isn't a good idea (partly because undesirable content will ultimately outnumber legitimate content)?

The impossibility of the assured annihilation of data is true of all protocols for data retrieval so long as client nodes are free and able to copy the data retrieved.

It's why removal of illegal content from the internet has been an abysmal failure.