What is this "Vo LTE" notification bar icon?
Now the icon is there all the time, occupying valuable notification bar real estate – and not providing any useful information in return, as far as I can tell.
What is this icon? What is it supposed to be telling me?
Can I make it go away? If so, is there a reason not to?
I think you have activated VoLTE service for that SIM, you can set in phone Settings.
It means Voice over LTE network. It is good to leave it like that because you get better voice quality during calls.
VoLTE means Voice over LTE. The icon notifies you that you are now able to phone over LTE. This means, it's not necessary in order to make a phone call to switch back to 3G (You cannot phone over normal LTE).
In short it's new and better. As far as I can tell you could disable VoLTE altogether, but I recommend you to simply live with it.