One of the systematic issue with Duo for me is the lack of the 'polite' you. If you do not know someone well, then you don't use the 'tu' form of the verb tu capisci but the polite form Lei capisce (written with a capital). Or so I have read. Anyway Lei capisce la ricetta is presently rejected by Duo.
So we get the habit of using the familiar form all the time.
But maybe my sources are outdated and this is OK?
Apparently it's no longer common to write the polite "lei" with a capital. This form gets introduced in later lessons and I think it's accepted thereafter.
What DL is rejecting is not "Lei" but "capisce". Since at this point "Lei" has not yet been introduced as a formal "You", I guess that is the reason why it's being rejected even though it's just as valid to use "capisce".
Duo uses capitals in the lesson you refer to. There is only one on "Formal You" and it actually has more on formal greetings salve instead of ciao. Interesting what you say about the capitals though - I wonder if tu is becoming more widespread. I bet ciao is. That's the internet.
I wrote what you write many times and I tried to correct them. Nothing to do. Not only: some "expert" wrote that "egli", for instance, is like the E. "thou".... Be sure: they will not learn the lesso.
why can I not use 'comprendi' here?
I'm not sure what the difference is between comprendere and capire. Both can mean "to understand," but only one is acceptable as an answer here?
Why "tu" and not "voi"?
Riuscire is surely the correct verb here?
Fun fact: the word used here, "capisci" (you understand), is where the term "capeesh?!" derives from. Literally meaning "do you understand?"
Seems whoever devises the Italian sentences has an odd conviction that the "voi" form is simply inappropriate for particular contexts. Surely, I could be telling more than one person at a given time that they all understand the recipe, say, if I were conducting a cooking class.
why can't I say "te capi la ricetta"?