I do had a horrible nightmare

"I do had a horrible nightmare." is a juxtaposition of past and present in the same predicate. I can't think of any logical reason to use it.

Drop the word 'do'. "I had a horrible nightmare." sounds OK.
Some may say that the nature of nightmares makes the addition of the word 'horrible' a redundancy. Perhaps it was a "particularly horrible nightmare".

"I did have a horrible nightmare." sounds like an event further in the past.
"I do have horrible nightmares." is possible. Sounds like a symptom for the psychoanalyst's couch. The word 'do' is superfluous in this case as well, IMO.
"I have horrible nightmares." Figuring my income tax might qualify.

He said, "I too had a horrible nightmare".

Well, that makes sense.

Yes, I like to mix it up a bit.

That's not really what WB asked about, Neo.




Some say a lot of really dumb things about the English language. English is full of redundancies but the style manuals just seem to pick on a few.



I'm not sure that's one of the uses of what appears to be an emphatic use of 'did'. Perhaps a case can be made for your idea.



The word 'do' is not redundant or superfluous if you want to be emphatic.

Well, that makes sense.

Thank you all.