When I'm on a trade run, and I see "Halt!" in system chat, I don't necessarly assume it's directed at me--especially when I don't see anyone in my radar. For all I know, it could be directed at someone clear on the other side of the system! My inclination is to continue on my way until and unless I actually see the person who is speaking. It would be really nice if pirates could actually address the pilot they would like to stop by name, or is that wishful thinking?
I've been wondering about something else, too...after going to a lot of trouble to make several "unlawful" factions neutral to me, I'm still getting pirated by them...what's up with that?