Sorry to contradict you again, but "toi" and "moi" are stressed pronouns and in this sentence those two persons are declared as rich, so they are subject of verb "sommes". The form "sommes (=nous) comes from the fact that when you add yourself to one or several persons, you consider that group including you as "nous"/we.
It would be the same if you said "Mary and Peter are rich", you would not need to add "they" in the middle: "Mary et Pierre sont riches".
What do you mean by 'stressed pronouns'? Is it acceptable in French to say "toi es riche" because 'toi' is a stressed pronoun?
I consulted a textbook "Grammaire Progressive du Francais", published by CLE International, Paris, 2003. I found these sentences in the examples and the exercises:
Page 10: "Paul et moi, nous sommes francais."
Page 11: "Jean et moi, nous sommes a Cannes."
Even this variant on page 16: "Ugo et moi, on est grands et blonds."
(Sorry I don't have a French keyboard.)
I think these sentences demonstrate cases in which the literal word-for-word equivalence between English and French doesn't apply.
pls look at this: http://french.about.com/od/grammar/g/stressedpronoun.htm and that: http://french.about.com/od/grammar/a/pronouns_stressed.htm
Basically, it is correct to say "toi et moi sommes riches" and "toi et moi, nous sommes riches", but the first one is closer to the English.
The construction with comma + nous is a further emphasis on the pronouns.
I disagree, unless we're speaking of colloquial English instead of regular English grammar. While DL allows "You and me are rich," that's not proper English. It's "You and I are rich." Language is fluid - and it seems that this is one of those phrases where people think both are okay, but formal English grammar (which is always good to know) says it should be You and I.
DL should not allow "you and me are rich". It's incorrect English grammar. That is a reportable error. We English speakers would not want to learn French that is full of grammatical errors either. Language is fluid, but "you and me are rich" is not the direction English is flowing.
Which non-formal translation, exactly, are you referring to? "You and me are rich"? That one is not only not formal, it is not correct. If it's not correct, formality is beside the point. "Toi et moi sont riches", however, is grammatically correct French, and translates as grammatically correct English: "you and I are rich".
I honestly don't even remember what or who I was responding to at this point.
I think I was saying something about his example of: "Paul et moi, nous sommes francais."
He was adding an extra "we" into the sentence that is neither in the French sentence or the English translation.