语法好的进来看看...Who is /was the compere?主语 为什么有人说的是who,如果主语是who的话

完全正确!
Who is /was the compere?这里the compere(主持人)是主语,who是表语.
I don't know who you are.这里you是主语,who是表语.正如你理解的那样,如果who是主语,按照宾语从句中疑问句用陈述句语序那就该是：I don't know who are you.
不过以下句子中what做主语,这个是英语习惯用法,也是重要考点：
I don't know what is the matter.
I don't know what is wrong (with him).
即what is the matter中what就是主语,what is wrong这个what自然也是主语.
欢迎探讨词法语法问题.

特殊疑问句的语序是Who is compere? (主谓颠倒）
但是当这个句子变成从句后语序就要变成陈述句的语序了。
I don't know who compere is. （主谓正常语序）

孩子，从句中疑问句要用陈述语序，在I don't know who you are. 这个句子中，I是主语，know 是谓语，who you are是宾语。Who is the compere.是个疑问句的单句，当然是疑问句的语序，而who是疑问代词，出现在单句中就是疑问句，不可以用陈述语序的。

who helped her? 此句中,who 是主语.象你说的那个Who is /was the compere? 一般认为the compere是主语,所以你说的很对, who are you中,you是主语

Who is /was the compere? who是表语。
I don't know who you are.who 是表语