yes, you can chase after a fleeing player. - mind, fleeing is not just thrusting out of your weapon range. so when someone thrusts so far away - like 6k that no weapon can possibly be fired and that you are CERTAIN that its not a tactic or a delayed joust anymore, you can of course chase / cruise.
but you cannot, if someone just puts some distance to you - like bombers vs. capital ships ..that usually take a long approach and refill their energy on their jousts, which can easily be like 2k away.
when in doubt - i would allways say "don t thrust".
after all, if someone is fleeing, its up to the char what he wants. - a gunboat defending is perfectly fine with the opponent fleeing, as the gunboat has won the fight and protected whatever it has to protect ( the retreating player must leave, so all is fine ) - winning a fight must not necessarily end up with one player dead.
anyway, i am sure most people can perfectly well tell retreating from jousting, when they are honest to themselves.
edit: i don t know about the opinion about that as a whole, but personally, i would include traders in the 4 hours rule - but only for death, not for retreat ( as that is what he s supposed to do ) - but as long as its not written in the official rules, - there s no need for a trader to stay away from any system after death or retreat.