“as common as muck”别理解成“像淤泥一样常见”，正确含义是低级的；社会地位低的；粗俗的。

【例句】
Considering she's wearing an outfit like that in public, she must be as common as muck.
考虑到她在公共场合穿着这样的衣服，她一定是社会地位低的。

It's not surprising that he shouted in movie theater. He's as common as muck. You'd better stay away from him！
他在电影院喊叫并不令人感到奇怪，他是粗俗的！ 你最好离他远点！