Explored areas should remain visible

To my mind, it's not logical that an area that has been explored should be returned to an unexplored fog once the player or Pet has already mapped the area.

Once explored, an area must be assumed to have been mapped by the player, and should remain visible to the player.

The problem, of course, is that if there was no node when the area was mapped initially, how then to keep the area visible without the player being automatically informed of the appearance of a new Node and its contents?

Maybe some sort of an alert, e.g., a highlighted area of a few squares with a question mark at the centre can be placed where a new Node appears in an already explored area. This would serve to remove the possibility of players automatically knowing the location of a new Node, but players are then alerted to the fact that a new Node has spawned in the vicinity, which makes for exciting play.