I found the registry entries that run this service.
Delete the following key and soft reset the device to remove that nag
HKEY_LOCAL_MACHINE\Services\App\Tasks\MannerMode
This key is also involved, although it doesn't seem necessary but can't be removed until the above registry is removed and phone is soft reset
HKEY_LOCAL_MACHINE\Software\HTC\MannerMode
You can use the PHM registry editor on your device or use
CeRegEditor freeware here to do it from a PC.
http://ceregeditor.mdsoft.pl/