Perhaps you were taught in school that you should comma off the adverb “too”? So for you a sentence such as this is correct:

I, too, will go there.

Or even this:

I will go there, too.

Both are strictly incorrect but this is a solecism so often taught to children that many people don’t understand why it is. Here’s the reason.

“Too” is an adverb almost exactly alike in function to “later”. You can often — if not always — replace “later” with “too” in a sentence and your new sentence will make sense. (The reverse is not quite true: the structure “I x verb object” doesn’t admit “later”. You can’t write “I later will write to you” for instance.)

I’ll see him later.

I’ll see him too.

Give it to me later.

Give it to me too.

Now, you’d never comma off “later” in those sentences. So don’t comma off “too”, which is functionally the same. Believe it or not, when words have the same function, they are punctuated the same way in a sentence.

So we’re clear that “Give it to me, too” is incorrect (and btw you don’t need a comma for “Don’t tell him either” or “they went there also” — you simply do not comma off an adverb in its default “unmarked” position in a sentence). But what about “I too will tell him”?

Well, not all that many adverbs can actually come between a subject and verb but try these sentences:

I very much like her.

I absolutely don’t like her.

I sometimes go there. You can see how ridiculous it would be to comma those adverbs off? And “too” is functionally exactly the same as “very much”, “absolu