[0x0]

One bitcoin is very much distinguishable from another bitcoin as they can be traced through transactions and wallets, with the outcome that some bitcoins might be rejected by recipients that are uncomfortable with certain source wallets or mixers.

[fragmede]

There's no way for a wallet to block incoming transfers. If someone sends Bitcoin to an address, the transfer will be processed by the network.

[0x0]

Yes but you could refuse to deliver whatever the sender is paying for. I mean you need to wait for 6 confirmations or whatever anyway before "approving" the payment transaction.