It actually depends on "difficile," not "ricordare." When you describe something as "difficult to X" you use "da." For example:
La parola è difficile da pronunciare. The word is hard to pronounce. ("Difficile" describes "parola.")
When "difficile" is modifying the action, you don't need a preposition:
È difficile pronunciare la parola. It is hard to pronounce the word. ("Difficile" describes the act of pronouncing.)
I'm still confused. The previous difficile example "adesso è difficile rimanere dentro". Isn't that the same usage here but no preposition.
Why is it "da"? The comments under this doesn't answer the question. I know that "da" means those things. So does "de", "di". Why "da"?
It just sounds good with "ricordare", don't try to apply to much logic to language. Practice, practice, practice and eventually "da ricordare" will just feel natural to you.
Another sentence using ricordare (I don't remember which one) used "a" in front of ricordare, not "da". How are we supposed to know when to use either?
That was probably due to ricordare coming after an adjective that requires it. "Ho dificolta' a ricodare questa regola", "E' difficile da ricordare". You can probably break it down to find which adjective "type" will use "da" and which will use "a", but honestly, it really just comes down to "it flows better". Unfortunately grammar is just a reflection of the language, a tool we use to try and understand the structure of a language, not the other way around. Grammar is essential to learn the logical framework on which we form language, but the nuances will always be illogical because people are fundamentally illogical.
Just keep using Italian enough and one day, after many mistakes, you will use the right prepositions in the right places, even for verbs you've never used in that way before. Just make sure to always check that you've got it right to avoid bad habits (this is how dialects are created, but if only you do it that way then you have created a new avocadohummus dialect that unfortunately no one else speaks!).
I read on the web version that "da" is used to give a somewhat passive meaning. In that sense, this sentence could be translated (it won't accept it because I tried) "His name is difficult to be remembered."
Couldn't "ricordare" also mean "recall"? I wrote that and was marked wrong.
Nobody seemed to have answered you. I did use 'Her' and it was fine.
I learnt that "da" roughly translates as either "from" or "by", neither of which could be applied here, prepositions seem so arbitrary sometimes.
Yes, it also can mean "to". When you go to a person's place and just use the person's name (or title), you use "da": , vado da mia nonna "I'm going to grandmother's" or vado dal dentista "I'm going to the dentist's" - but vado a casa di mia nonna. You don't use da if the noun following it is not a person.
An interesting video discusses this and the use of prepositions a and di. https://www.youtube.com/watch?v=KmL4V_d-XRc
(Goto 5:35 in the video for the discussion of da = "to")
I really like the videos done by this particular vlogger, Lucrezia. She speaks very clear Italian at a reasonable pace, uses fairly simple grammar, and repeats a lot of phrases with explanations and body language to help explain what she's saying. After 2+ years at Duo, I find that I can understand her about 90% of the time, which is gratifying. If I get lost, the subtitles really help.
Can't "suo"/"lei" be used for "you" as well, but in a polite form? That's what I've been told but I got marked wrong for it!
You are right, it can. The only thing you have to pay attention to is, that you always capitalize the words "Suo" and "Lei" in the formal you. So that's probably why you got marked it wrong here.
I don't recommend using the formal Lei. Duo frequently does not recognize it, however correct it is.
Just don't get this. Ricordare means to remember so why 'da'? I shall continue the battle but think my Italian will be restricted to ordering in bars and restaurants. And knowing the names of animals and fish!