章振邦语法书上说：某些连接副词consequently,furthermore,hence,however,nevertheless,therefore等也用作并列标记，在这类副词之前要用分号，而不可以用逗号。
比如：
1）以however 举例我发现韦氏词典上：
Id like to go; however, Id better not. [=Id like to go, but I should not]
The forecast is bad. Its possible, however, that conditions could improve.
Sales are up this quarter. However, expenses have increased as well.
为何上面3句however前有些是用了; 但有些的仍然是, 为何呢？
2）I had arrived early as was my habit; I, therefore, felt priviledged to take my leave without delay.
这句中therefore和I 前用了; 请教老师as was my habit中的as 是什么词性，作什么成分？ 谢谢！
可以换成as it was my habit, 即加it吗？
1 第一，我不相信章振邦会说连词副词也用作并列标记。我估计这是你曲解了章振邦的意思。并列标记意味着在语法上前后二个结构为并列关系。比如并列连词and,but等，与分号为并列标记，表示前后二个分句为并列句。但连接副词并没语法上的并列标记用途，它只是在语义上表示前后二个分句之间存在某知逻辑关系，但在语法上，连接副词是后一个分句。这就是为何连词副词所在的分句与前一个分句要用分号，或者前一分句用句号，连接副词所在的分句另起一句。一句话，连接副词不是并列标记，假如要和前面的分句并列，就需要分号作为并列标记。
连接副词一般与分句其它部分用逗号隔开。最容易见到的是坐落于分句句首，其后用逗号。但也可以坐落于主语和谓语之间，前后用逗号隔开。偶尔连接性状语也可用于句末，前面用逗号隔开。
2 韦氏词典的例句都是标准的连接副词使用方法。
Id like to go; however, Id better not. [=Id like to go, but I should not]
however用在并列句中，分号为并列标记。
The forecast is bad. Its possible, however, that conditions could improve.
连接副词用在独立分句中，前后用逗号隔开。
Sales are up this quarter. However, expenses have increased as well.
连接副词用于独立分句中。
3 I had arrived early as was my habit; I, therefore, felt priviledged to take my leave without delay.
连接副词用于分号连接的并列句中，插入主语和谓语动词之间，前后用逗号隔开。
as was my habit 为方法状语从句。as引导的方法状语从句是比较分句范畴，所以as有哪些用途好似其它比较分句，分句使用缩减形式为其常规。
as was my habit 假如补全（仅仅处于讲解的目的，实质不可补全）的话：
= as it was my mabit that I would arriveearly 即从句省略了形式主语it和that引导的主语从句。因为整个主句为比较项， that从句的内容为比较对应项，所以that从句是不可补全的，需要省略。
