Okay I've searched and didn't see anything. I read the similar theads and nothing was relevant to this...
This will only work if the players name is in violation of the naming policy, which is like 30% of the userbase I'd say.
It's simple, petition the name and /friend them. You can then see when the players name is changed to take the name. Just create a new character with that name. There is normally not a block on changed names, I've done it quite a bit.
Now you could write the person after you take their name for some fun but chances are they'll just petition you back, so don't do it if you like the new name.
Enjoy!