Duolingo's translation of mom and dad...
I still don't really get why Duo would uses the words 'otec' and 'matka' for normal use of mom and dad. Don't know if I'm right, but have heard that those words are the most formal way of saying mom and dad, and you would never use those words for your own parents. I think that will be worth noticing, that you would not use that for normal everyday use of mom and dad.
Anyone know if I'm right?
"you would never use those words for your own parents"
That is completely false, as you can quickly check by searching "má matka", "moje matka", "můj otec", "matko", "otče" in the national corpus, on Google Books and elsewhere. Let's not forget https://youtu.be/9OyQ6Er73Kk?t=33 (this usage is obviously a joking one).
I would not use the vocative "matko" and "otče" to call my own parents, it would be awkward, although it is not completely unheard of even today and in literature you will find many examples. On the other hand I would use "můj otec" "má matka" when writing officially and formally about my family relations.
"Otče" today gets much more usage to address the God or a priest or when used jokingly.
mom - máma dad - táta mother - matka father - otec Yeah, we don’t use it. Matka and otec sounds harshly.