Using the conditional in a question

Question

Comparing the following sentences, what are the differences between them?

Cosa sapresti dirmi su Luigi Rossi?

Cosa sai dirmi su Luigi Rossi?

Since it is a question, I don't see any difference between those sentences. Furthermore, I don't see any reason to prefer the conditional to the indicative mood.

Is there any difference between those phrases?
Does the first, for example, imply any willingness from the person who answers me? Is it a more polite way to ask a question, since it would be understood as Cosa sapresti dirmi su Luigi Rossi, se mi volessi rispondere?

Answer 1

Using the conditional form is more polite and it is sometimes used as an alternative to add other pleasantries like “per favore”.

The crux of the question is that by expressing a question (or an order) as a hypothetical question, one (theoretically) leaves the answerer open to ignore the question. Of course, nowadays everybody understand it's a kind form, but the answer is not optional!

I think that the missing condition should be understood as “se fosse possibile”. For example:

• Cosa sapresti dirmi su Luigi Rossi (se fosse possibile)?
• Vorrei un caffè (se fosse possibile)!
• Mi daresti una mano (se fosse possibile)?

Seen as this, it is similar to other European languages, for example “S'il vous plaît” in French, “se faz favor” in European Portuguese or “if you please” or “if possible at all” in British English.

Answer 2

The Conditional in a question adds a different flavour. It can be more politeness, like Skilwz suggested, but not always.

Keep in mind that in Italian if you want to be polite you can use the third person singular (or the second plural if you are from the South).

I can imagine an university professor asks a student:

Cosa sa/sapete dirmi su Luigi Rossi?

But if I hear (conditional, still third person singular)

Cosa saprebbe dirmi su Luigi Rossi?

Then I can guess that the professor is giving a last change to his student or he is just mocking him.