Quote Originally Posted by Hanna View Post
When you add "indeed" you are just sounding more British, formal and a bit more sophisticated (it's a more middle or upper class way of speaking).
You would not say that to somebody in your family or a good friend.

No need to use ["indeed"] as a non-native speaker of English...
I have to say that I think Hanna's advice in this thread has been excellent, and I agree with her on almost every point (including this one).

But I wanted to add that if you're a non-native speaker who has reached a level where you can read P.G. Wodehouse's "Jeeves and Wooster" stories in the original, then you can certainly use "indeed" for comedy purposes, to do an impersonation of a very proper, erudite British speaker like Jeeves: "Oh, indeed, sir."

However, you should be aware that the word does tend to create a humorous tone of "mock-formality" (that is, subtly making fun of aristocrats, but in a hyper-polite way, as Jeeves often does with Bertie Wooster).

Anyway, I wanted to mention this because у меня четырехлетний племянник абсолютно ОБОЖАЕТ это слово, и он всё время говорит "Indeed!" с означением "да". (I've got a four-year-old nephew who absolutely adores this word, and he's always saying "Indeed!" to mean "yes.")

As far as I can tell, мальчик приобрел такую привычку со своего папы (the boy acquired this habit from his father).

My sister's husband is in some ways a stereotypical "I.T. guy" who plays online games like "World of Warcraft", has many friends involved with the Society for Creative Anachronism, and watches a lot of British comedies like Monty Python and Blackadder. So, мой зять (my brother-in-law) uses the expression "Indeed!" in his speech more often than most Americans do, and my little nephew copies his daddy. (Although he doesn't understand yet that the adults around him want to laugh when he says "Indeed!")