I’m reassured by the many peoplewho, out of concern for those who are old, frail or immunocompromised, have chosen to protect people like me, often at a huge cost to themselves.

请问大家这里 often 引导的这部分作定语修饰前边的 many people 么？ 

可是 为什么会有逗号隔开呢？  并且为什么放的如此靠后呢?