I think we're missing something here. CmdEcho? Are you sure? That's not going to affect the text displayed from inside the LayerP command is it? I thought that would turn on/off the display of issuing the LayerP command onto the command-line.
Now NoMutt may have an influence ... I'd think.
But!
I think we're going too far with this. The code tells me there's a nil that will display on the command line. And as people generally make the command-line as small as possible, this probably scrolls the LayerP's message off-screen.
So try modifying your code thus:
(defun c:lp ()
(command "_.LayerP")
(princ)
)
That should sort out the nil at the end of the "shortcut".