NPCs have a different coloured blip on the map, and are also at the very bottom of the widescan list. Dark Ixion and Sandworm both appear as the last monster on the widescan list, just above NPCs. I've scanned and claimed ixion enough times to know. I believe most other roaming NMs appear at the end of widescan as well. So all in all I don't see your second point as much of an issue. As far as your first point, a text filter system would be awesome, but I think it'd be far too much trouble to implament.