There is no problem with allocating one 127.0.0.0/8 to every interface on your host, because 127.0.0.0/8 is only ever accessible to the host itself. So even if you have multi-homed a single routable IPv4 address to 2 NICs on your server (for redundancy), you can still assign 127.0.0.1 to the first and 127.0.0.2 for the second, which you can then use to bind a port to a specific interface in the pair. (I don’t know if anyone actually does this.)