Here is the tutorial

1. Sign in, Go to your comment and delete it.

2. Press X on the green grid button to change the layout of keyboard to the small keyboard.

3. Press X on the tool wrench. A prompt saying 'Single tap' will appear. Press X again.

4. Press X on the ABC2 button. Press Triangle. Press X on the .@/+1 button. Press Triangle. Press X. Press Triangle. Press X. Press Start then Start.

I'll write it out in short like a oldschool psx cheat:

Press X on the GREEN GRID BUTTON, Press X on the SPANNER, Press X on SINGLE TAP BUTTON, DPAD DOWN, DPAD RIGHT, X, TRIANGLE, DPAD LEFT, X, TRIANGLE, X, TRIANGLE, X, START, START.

If done correctly it should show: A . ..

Now sign out then sign back in (You may need Auto Sign in on), Now your appearing offline to everyone else. You wont be able to receieve Message, Game Invites, Chat Invites and well anything involving recieving, But i think you can send messages.

You'll notice when you sign in it will just be your PSN ID that shows for a while, then all your friends load but are offline and have no last online time, and to make things back to normal and go back online just delete your comment.

Source: http://community.eu.playstation.com/t5/PlayStation-3-General-Discussion/MUST-SEE-How-to-sign-in-to-PSN-and-appear-offline/td-p/13476877

I did it and it works. Now I can sign in and ignore messages without being rude. :)

I've actually been doing this with my PS3 and Xbox 360. I actually do this all my messengers (AIM, MSN, Yahoo, etc). I love being invisible

This explains why a couple of people on my friends list always show up a the very bottom with no "last seen" information.

You anti-social super nerds, you. I'm surprised you even have friends lists!

:P

This is why I pay for my Xbox Live.

Jay520 said: xLeftyx said: I've actually been doing this with my PS3 and Xbox 360. I actually do this all my messengers (AIM, MSN, Yahoo, etc). I love being invisible How have you been doing this with the PS3 already? You already knew this trick?

Yeah, I've read in a Playstation community before also, some months ago; but yours look a little different for some reason. I hated having to log online (PC) and check to see which of my friends are online before I log on to my PS3. I wish Sony would remove the public profile online also. That's why I don't just give out my PSN ID 'cuz of that.

Either way, at least Microsoft makes this readily available.

Lolwut?

I really don't see the use of this...
...yet, if some people find it an interesting thing to do, I wonder why Sony didn't offer it already.