Yeah Sock, the setup switch if for people like yoiu who want to emulate the non-admin mode
. As for checking for Plus!, as Lizard Man said, it would be an invasion of privacy, that'S why /ping is there and that'S why peopel can disable it if they want
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As for setting a sound for one time, you can associate the sound you want to Plus! notifications so you could just set the one of your choice and ask Plus! for a notification next time the contact signs in (Messenger Plus! Extra menu).