网友应该主语句首大写和句末用句号。
One argument that you tend to hear a lot from the pro-tipping crowd seems logical enough.
句子主干为:One argument seems logical enough.
that从句为同位语从句,而不是定语从句。同位语从句为名词性从句,that为连词,在从句中不作成分。引导定语从句的that为关系代词(偶尔为关系副词),需要在从句中作成分。本句中,that在从句中不作成分:you 主语 tend 谓语 to hear a lot from the pro-tipping crowd 宾语。主谓宾齐全,不缺成分。that没作成分。同时that从句的内容就是argument,从句与argument为同位关系。