there is a user named 'Helper' who can do this. i met them a few times, we're quite good friends. only thing is, kovu gave them this special ability, her and only her.... :/
this i very much doubt
but i agree with this. not so much for your actual user to be invisible, but to appear invisible on friends list and on the map. like already stated by a lot of people, i find it bothersome that i have to hide out on other accounts just because of wanting to avoid whispers and the like from friends/group members.