although I prefer the construction, 'nic nie rozumiem', I just think it flows better.
#metoo, Ms Atch. What I meant was that Roz's phrase lacked another negation, and merely the single negation (as in English) was applied instead. For that reason and for another reason that it was wrritten as one word, I did not read her nick properly for quite a long time. I was reading it as something like 'rozumnienić' or 'rozumienić' taking it as a verb in infinitive because of the ending -ic (ic). So you can now see how important for the Polish speaker the double negation is and without it even the meaning of the phrase may be lost.