Hm, so no one really knows, huh?
Well here's what I got so far.
33 groups of 5: open channel, greetings (non-talkative), open channel (hostile), unknown, open channel (mission escort), open channel (carried ship), unknown, unknown, unknown, unknown, unknown, unknown, can't afford payment, greetings (hostile), won't assist (unnecessary), coming to assist (combat), won't assist (busy), won't assist (don't want to), assist if paid (combat), won't assist (ridiculous), accept mercy bribe, deny mercy, won't assist (player escort), mercy if paid, mercy if paid (mean), won't assist (AI escort), unknown, mercy for free, assist if paid (service), coming to assist (service), reject lower price (mercy), reject lower price (combat/service), unknown.
Tell me if any are wrong or if you know what the unknowns are. There's actually 38 groups but I decided the last 5 are unused (UE R&D is right which means the next STR# is completely unused too). I couldn't get ships to assist in combat (the flag in the rank won't work <_<) so I'm not sure about the coming to assist and assist if paid that I've labelled as combat.