Is it correct to use the word "do" twice in a row? For instance; "I do do that" or would you say "I do that"? "You do do that" or "You do that"?
Which is correct, or are they both correct?
Using "do" twice in a sentence, even in apposition, is not grammatically incorrect.
If you can say
which you certainly can, then you can also say
Note that in my first example, a single do won't suffice. It would be awkward or at least archaic to say
No modern-day speakers would ever say such a thing.
The construction even appears in the song "You Do Something To Me" by Cole Porter:
And, for a laugh, let's close with Sting's use of multiple *do*s:
Obviously that's not the same grammatical use case, but it does have a logic all its own.
In general "I do that" is enough. But if you want to emphasize that you "do" that you can use do twice. In question the first "do" should be on the first place. Do you do that? That is the only right variant.
It is the first use of the word 'do' that is incorrect in the sentence "you do do that". The correct response could be that "I have seen you do that" or "I have noticed that you do that"
I do that is sufficient, although when wanting to emphasize the fact that you really DO do something an extra do is added. So for instance if worded differently this sentence could be constructed like this I really do this or I really do do this= one of the do's here is used for emphasis to add definition to the fact that you really do that something.
She phoned Peter= fact
She did phone Peter, I know she did= fact, but the speaker sounds as though trying to convince the listener that she really phoned Peter and it's not a lie.
In the second sentence as the past tense is used the do is changed to did.