honestly, SL is something like a "goodness" value. killing does and never should make you a better person. while killing enemy runners might be required sometimes to achieve a higher goal, killing innocents or friendlies is bad. killing is always bad, but because it's not always that simple non-friendly kills often do not result in you being seen as bad (by the society/faction you are in).

killing certain runners could positively affect your symp with all factions that have a allied/neutral status with you and are enemies of the faction in question, but should also negatively affect your symp with the faction of the victim and their allies.

killing simply shouldn't be rewarded in any case. that's simple ethics imho. it should never affect your sl in a positive way.