In fact, this sentence "Eu não lembro disso" is grammatically incorrect in Br-Pt as well. Based on the information in the links below provided by Brazilian authors, the correct sentences are supposed to be:
- Eu não lembro isso = I don't remember that.
- Eu não me lembro disso = I don't remember that.
"lembrar" goes without "de", or "se lembrar" goes with "de": "O verbo “lembrar” admite algumas construções, cada qual em uma situação diferente", "quando o verbo é pronominal (lembrar-se), seu complemento é introduzido pela preposição “de”", "O verbo “lembrar” também pode ser um transitivo direto, construído com complemento sem preposição"
https://portuguessemmisterio.com.br/2016/02/23/eu-me-lembro-disso-ou-eu-lembro-isso/; https://educacao.uol.com.br/dicas-portugues/lembrar-direto-ou-indireto.jhtm; http://g1.globo.com/educacao/blog/dicas-de-portugues/post/eu-me-lembro-disso-ou-eu-lembro-isso.html
I suggest native speakers/moderators research clearly for the correct grammar before passing on inacurate grammatical information. Native colloquial ways of speaking or experience often do not go with correct grammar. All those colloquial phrases are better to be used as alternative translations, not the principal translations. It will be much more appreciated. Thanks. 11/04/2017
As a native speaker from São Paulo, I would only very rarely use the pronominal verb, even in formal contexts. I don't think it's actually colloquial to dismiss the pronoun if it happens more often than what the books tell us to do.
Well, it's not because we Brazilians leave out the pronoun to mean the same thing that we can drop the preposition and keep the same meaning. It just doesn't work like that.
Eu não lembro isso, without the preposition, means I don't resemble that:
Ela lembra a minha mãe = She resembles my mother
Ela lembra da minha mãe = She remembers my mother
Ela se lembra da minha mãe - She remembers my mother
Even though the most grammatically correct alternative is to use the pronominal verb + preposition to mean "remember" - as you pointed out, I don't think Duolingo is concerned with teaching prescriptive grammar. It focuses primarily on how native speakers actually speak because you don't want to engage on a conversation sounding like Professor Pasquale giving a lecture.
@Serraesilva stated that in Portugal it would sound strange not to use the pronominal verb, but this course intends to show how Brazilians go around this sort of constructions.
So, using a pronominal verb in a conversation wouldn't really change what you're trying to convey if you do want to mean "remember". "Resemble/remind of", on the contrary, will never take on a preposition although it can admit the pronominal form just to specify who is participating in the verb "lembrar":
Nós lembramos aquele grupo = We resemble that group
Nós lembramos daquele grupo = We remember that group
Nós nos lembramos daquele grupo = We remember that group
Ele me lembra um amigo nosso = He reminds me of a friend of ours
Eu te lembro alguém? - Do I remind you of anyone?
Additionally, you can use "lembrar" in the sense of "remind, inform, give a heads up":
Eu os lembrei (de) que haverá prova = I reminded them that there will be a test
Eu lembrei os alunos (de) que haverá prova = I reminded the students that there will be a test
I think in this context including my quoted links, we are only talking about "lembrar" as "to remember + noun.". All the links are using "lembrar" both with and without "se ... de" to mean "to remember"; unless you are saying those language experts are wrong, and your colloquial languages are more correct than the actual grammar. I think I'm obliged to repeat that those authors of my quoted links are also Brazilians, they are not from Portugal. I also read in other DL threads where Brazilians commented these two (either "lembrar" or "se lembrar + de") are the correct forms.
I had not known that "lembrar" can mean "to resemble" untill I saw it in this link: https://en.wiktionary.org/wiki/lembrar#Portuguese. The link also says "1. (optionally takes a reflexive pronoun, transitive with de) to remember"; it again shows that you can use either "lembrar" or "se lembrar + de", but in no situation ever show that you can use "lembrar + de" without "se" to mean "to remember". I certainly believe the colloquial way is more convenient in daily speech like the one shown in this exercise. Exactly like how you use "pra" colloquially, however is completely unacceptable by DL.
I don't really want to argue with you about your opinion on the approach of DL Portuguese course or its actual approach as I believe many people would agree how contradictory DL course contents are.
I also read in the comments that Brazilians mix conjugated verbs all the time in colloquial speech. I doubt that everybody wants to learn wrong grammar first. I reckon it is always preferable to firstly pass on the correct current grammar in a language course, particularly in a language course with millions of learners coming from different background, let alone passing on the wrong grammar. It is always good to know the colloquial language, but it is up to each individual to adopt either colloquial or formal speech they prefer.
I don't mean to undermine whatever these "language experts" have to say about grammar nor do I want to induce Portuguese learners to ignore grammar rules.
That being said, lembrar de and lembrar-se de are both equally good in everyday speech, even though lembrar de, the non-pronominal form, is way, waaay closer to what most Brazilians use, formally or not.
Of course it is important to know the rules but you've got to have in mind that Portuguese, as currently spoken in Brazil, does not consider the non-pronominal form any less correct than the pronominal one. And it's even more important to know that grammarians do not make a language the way it is, speakers do.
Also, you did compare lembrar de to pra, as if both would fit in the same category. Pra, meaning para a, is only acceptable in informal contexts, such as conversations, WhatsApp messages... Lembrar de, without the pronoun, can be used in a variety of contexts, including essays or school works (unless you are taking normative grammar classes).
So, again, Duolingo focuses on how Portuguese happens in real life. If "Eu não me lembro disso" were the most "correct" form, Duo would probably use it, or else other native Brazilian Portuguese speaker would already have pointed it out (just like @serraesilva did when noticed it "lacked" a pronoun in European Portuguese).
I understood language evolves. Colloquial languages happen because they are convenient, but often grammatically incorrect. As I already noted that many Brazilians themselves also admitted that there are loads of grammatical errors in daily speech. I don't think there is a point to argue about that. Speakers do influence a language, but grammar still has to be followed by speakers, particularly in formal context.
Indeed, I believe "lembrar de" as "to remember" is an informal speech, like "pra"; it might be considered as correct grammar as time goes, who knows. If you had a better look at the link: https://en.wiktionary.org/wiki/lembrar#Portuguese, you would have seen "lembrar de" does exist. However, it means "to remind", not "to remember". Based on the first three quoted links written by Brazilians, I do believe currently it is grammatically incorrect for Brazilians to use "lembrar de" itself to mean "to remember". If it is correct, those links would have never existed in the first place, I wouldn't have seen the comments where Brazilians say "lembrar de" was incorrect grammar as well. You seem to be very reluctant to believe what I said before that there were Brazilians who had already pointed it out, let alone the authors of those links are Brazilians, not Portuguese. Here is one link: https://www.duolingo.com/comment/415720, where Paulenrique pointed out "Actually, the correct way is "lembrar-se de": Como você se lembra disso?"", which means "lembrar de" is incorrect grammar. There is another DL link where a Brazilian used "esquecer" to give the example ("lembrar" and "esquecer" have the same grammar rules). He stated that "esquecer" and "se esquecer ... de" are formal speeches; it again shows that "esquecer de" is informal speech, so is “lembrar de”. I can't find that link though...
I thought you knew that there are a lot of errors in DL courses. I also thought that you knew that DL contributors are not language experts, but language lovers. Well, again I do not agree that DL focuses on Portuguese happens in real life; this point itself is contradictory. Because if it does, it should have accepted "pra" at the least instance which is used far more often than "para a" in real life. As I already noted, DL contents are contradictory in many aspects. 14/04/2017
Disso, literally means de + isso. That is of + this.
But remember that preposition rules are very different between languages, and there is hardly a good rule to understand how they work.
Here, the trick is in the verb. "Lembrar" demands the preposition "de" in Portuguese, and that's why "disso" is used instead of just isso. In English, "to remember" doesn't demand a preposition, and then the translation simply throws it away.
If the verb didn't demand a preposition, like "querer", then it would be "eu quero isso".
Why does "lembrar" demands a preposition? The explanation is the same as to why "to listen" demands "to" preposition. ....well, there is no explanation.