介词短语作定语修饰

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

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

可是 为何会有逗号隔开呢？ 并且为何放的这样靠后呢?

often at a huge cosplayt to themselves 并非定语，而是补充性状语修饰不定式to protect，表示方法。因为是说完话之后补充的状语，所以用逗号隔开。