Mortality rates for young people are not negligible, and we don’t know either the long term health impacts of a severe episode of the virus or even whether catching the virus gives immunity.
Its very likely and we kinda know that catching the virus gives short term immunity. Longer term is unknown.
for young people, it's less deadly than the flu.
Citation needed. Everything I've read says that it's significantly more deadly than the flu for all ages and that more importantly the error bars on any mortality number are absolutely huge.