These are all arguments that make no sense, because each of them differs in essential ways from what we're discussing here.

The only point is that twit filters are pervasive and generally accepted- even though we know very well that we are being filtered when we call our doctor, lawyer, electric company, or Bill Gates. ;-)

Of course I take your point that if we decide to avoid Aunt Beth's phone calls, she doesn't hear a "your party has chosen to block your call" message.

To avoid such a message in UT would involve posts being sent and then hidden from people who have asked not to see them. If those wishes are respected, still the sender will be ignored but now it will be in full public view- similar to your scenario of one employee ignoring another at a social occasion. Obviously that would not be desirable. I'd also be concerned that if twitted posters are able to send messages that are visible to everybody except their target, that would create opportunities for contrived mischief- again in full public view. This contrasts with the relatively private twitting consequences under the current regime.

I can see that twit filtering is perceived by some as being similar to the "shrouding' in "The Paper Chase," except that online twit filtering tends to be a private matter which usually is broadcast by the twitted party, not by the twitter.