Given the following code:

@EventHandler
public static void onBlockPlace(BlockPlaceEvent e)
{
		if(e.getBlockPlaced().getType() == Material.WALL_SIGN)
		{
			Sign s = (Sign) e.getBlockPlaced().getState();
			s.setLine(1, "NewShop");
			s.setLine(0, "[Buy:Sell]");
			s.update();
		}		}

the sign is placed and the interface comes up for the player where they can enter their sign text..   This pre-populates the sign text.   However if you change the text then click done the text is not modified and the following warning is printed to the console.

23.09 23:34:25 [Server] WARN Player dniym just tried to change non-editable sign

This also seems to have the side effect of preventing a SignChangeEvent from firing.

	
@EventHandler
public static void onSignEdit(SignChangeEvent e ) {
		System.out.println("Edited a sign");
	
}

If the sign is NOT pre-populated the sign change event fires as expected however it does not fire if the sign is populated on block place, regardless of if the text was edited by the placing player or not.