I've seen some news reports that suggest covid-19 can cause longterm/permanent damage to the lungs. does that happen to everyone who contracts it or just those with more serious cases? would those who are otherwise asymptomatic be at risk for that?

Hard to say/unlikely: Since the affliction has only been around for 4+/- months it is hard to speculate what the long term implications are. It takes months to accumulate data and years to demonstrate long term effects. If this behaves like most similar lung infections those with the worst initial symptoms & care needs would have the most potential for scarring/lung damage. Those with few or no symptoms would not.