I've been wondering if this is a dialect thing. The male voice makes a sound that sounds more like /sh/, especially in consonant clusters (similar to in German) and at the end of words (similar to in Portuguese), whereas the female voice always clearly says /s/. https://en.wikipedia.org/wiki/Dutch_phonology#Obstruents indicates that /s/ and /z/ can be retracted in Netherlands dialects, which would make them sound more like /sh/ and /zh/ to English speakers' ears.
The mistake is in the course. The Dutch "Het dier eet een sok." doesn't in itself distinguish between "The animal eats a sock." and "The animal is eating a sock." However, a sock isn't very large, and socks aren't around to eat in large quantities, thus the creators of the course have chosen the present progressive form, "The animal is eating a sock.", talking about what is happening at the moment, as it can hardly be present simple "The animal eats a sock.", something that'll stretch over time. Yet, now picture (if you can), a harvest mouse living in the Giant's laundry basket in the winter time. There are plenty of clothes there, but clothes don't have all that many vitamins, and shirts and pants have a terrible taste. So, the mouse prefers morsels and other bits of food that can usually be found in the Giant household. But if the mouse cannot find better food, the animal eats a sock.
If you get the same answer again, report that your answer should be accepted as well.
The point is that "De leerling leest alle commentaren." could be translated both as "The pupil reads all comment." and as "The pupil is reading all comments." Which translation is preferable depends somewhat on the context. But if the pupil doesn't read all the comments, than he'll ask the same question I answered last week.
The contributors to the course picked the present continuous as the more likely answer. Grammatically, there's nothing wrong with using the present simple instead; I would even advise you to forget English present continuous when translating a Dutch sentence that uses present simple. Stick with present simple in both languages until Duolingo introduces the Dutch version of present continuous. In this case, that advice gets you into trouble, apparently, so if your answer is refused again, report that your answer should be allowed as well.
Sorry, that's one of the hardest parts of Dutch-you've just got to have it memorized. But if you know the de's and the het's of common words, they still hold true for compound words containing them (for example, "het huis" and "het ziekenhuis" are both het's because "huis" is contained in "ziekenhuis", which means "hospital"). Hope it helps