Inconsistent word order
I wouldn't consider myself and expert in Latin, in fact I only took classes back at school but didn't use much Latin for 8 years now, but always tried to keep it alive. So I was very eager to start the Duo course to fresh it up and maybe contribute a little bit myself. There's particularly one thing that seems to be a regular issue and instead of reporting it case-by-case I've decided to start a discussion.
So far what I've noticed is that often the sentence structure taught is inconsistent. Sometimes, the word order will be like in English, e.g. Philadelphia est urbs. However, I am used to putting the verb at the end of the sentence, which is actually the more "Roman" way, so it would usually be Philadelphia urbs est. Often the variant with the verb at the end of the sentence will be declined, but sometimes it's accepted and some other times it's even the only correct solution. I find it a little bit frustrating to guess which word order Duo will accept, because I'm often deciding between what I was taught is correct and what I guess Duo wants to hear. So far I'm still reporting every case where I'm positive a sentence structure with a verb at the end should be accepted, but I thought I also wanted to make a heads up about that and hear everyone's opinion.
That being said I'm totally digging the Latin course! The long waiting has finally paid off (I remember discussions asking for Latin from back in 2012)!
Well, you're not wrong that Latin is predominantly SOV word order, placing the verb at the end. There are two things to note, however.
The first is that the verb esse (to be) usually goes in SVO order, like in English. But the SOV option is also right, and goes hand in hand with the second thing.
That second thing is that Latin is a heavily inflected language, which means much of the meaning is conveyed through the forms of the words. What this means is that Latin doesn't rely much on word order to convey meaning, which in turn results in Latin having very free word order (although it is predominantly SOV). So both "Philadelphia urbs est" and "Philadelphia est urbs" are correct. So if you find any such translations that aren't accepted, go ahead and report them as correct (provided they have no typos, of course). :)
Volgav vitsenanieff nivya kevach varatsach.
I think when you say "Latin doesn't rely much on word order to convey meaning" you mean, "word order serves a different, less literal kind of meaning". These shades of meaning include:
emphasis: whatever is first, or maybe last, is emphasised
placing the verb first can imply a meaning a bit like "There is" (or whatever the verb is "there was", etc
then there are a bunch of style conventions around reflecting word pairs
then there is rhythm and cadence in poetry which is another level of meaning
There are also some rules of thumb like multus, magnus, parvus, type adjectives preceding the noun, where adjectives normally go after.
In short Latin word order is not random, or meaningless but also doesn't convey the kind of linear meaning that you get in English or modern Romance languages.
• urbs Philadephia est: Philidalphia is a city, (not something else).
• Philadelphia est urbs: Philadelphia is a city (as opposed to some other one or some other thing)
• est urbs Philadephia: maybe that's the city, Philadelphia
- est Philadelphia urbs: something like *that's Philadephia the city *
Feel free to correct me on these interpretations if you think they are wrong.
Putting stress on a word by moving it to the front is called "fronting" and is a thing in many language, including ones that are not inflected.
But I think that you are missing the point of what the person was trying to say, which is that none of these slight changes in meaning due to word order affect any of the sentences within this course - within this course, none of these slight changes in meaning due to word order affect any of the sentences (see what I did there) because putting stress on words, as far as I have seen, is not a thing being taught within the course. Additionally, the english translations would have to make this meaning apparent during the translations.
I do think, however, that it would be good to dedicate a skill somewhere in the tree to teach this though.
"There are also some rules of thumb like multus, magnus, parvus, type adjectives preceding the noun, where adjectives normally go after."
I found out this is enforced here, at least for multus. However, is this something that was true in Classical Latin? Because otherwise one can find plenty of the opposite. My high school textbook literally introduces the word "parvus" in this sentence: "Amicus in opido parvo, sed pulchro laborat." Is it wrong?
Here's one explanation: http://rharriso.sites.truman.edu/latin-language/latin-word-order/
In your example,Amīcus in oppidō parvō, sed pulchrō labōrat the speaker is contrasting 'small' with 'beautiful'. If they hadn't placed the two words together 'parvō, sed pulchrō', the contrast would not be as apparent (a friend lives in a small town, but beautiful) even though it makes more sense in Latin than English. So it's done for contrast I would say.
You could further argue that "small but beautiful" now serves a descriptive purpose.
Maybe it is terms like the names of kings like "Karolus Magnus" that confused me. I just checked Vita Karoli Magni and magnus does indeed come before of the noun there, although not exclusively. And perhaps also biology where one often sees these words as a species name that comes after the generic name for other reasons.
This kind of syntax is used for names. In Latin you can see it for example in Gaius Iulius Caesar, where Gaius is the name and Iulius qualifies it (which Gaius, of which family?) while Caesar qualifies them both (which Gaius Iulius?)