Can "either" be used as an adverb, and if so does it require, allow, or prohibit the use of a comma when so used?

Can either be used as an adverb, and if so, does it always take a comma when it is? And is the following statement correct in congruence with my question? I believe there is some mistake that I don't perceive:

He never talked to Sanena, and doesn’t like her either.

Another thing is that I feel this sentence of mine should have either without any comma, but somewhere in a sentence I have seen a comma placed right before the word either.

Could someone please clarify for me which particular conditions lead to using a comma before the word either?

Solution 1:

Either can definitely be used as an adverb. It does not always have a comma with it. Your example sentence is grammatically correct:

He never talked to Sanena, and doesn't like her either.

The meaning of either is in addition. It is used in negative sentences to add emphasis.

Here is another example sentence using either as an adverb:

Many hotels in Bangkok are beautiful and not expensive either.

(notice: no comma)

Here are two example sentences that use either as an adverb and a there is a comma in each sentence:

The food in that restaurant is awful, and the tables aren't clean either.

I have never been there either, nor do I want to go.