Default nameplates have the ability to fade based on whether they are in your characters direct line of sight. I would love to see such an option in this addon as well.

In terms of performance impact, it's non-trivial to provide this as well as the other custom fade rules, as the API doesn't give enough information or ability for us to efficiently reimplement it. That goes for the distance fading, too.

For that reason I don't want to put it in core, but you can find a custom script for it here: https://github.com/kesava-wow/kuinameplates-customs/blob/master/custom.los-fade.lua