I think that responsibility is up to the course moderators, since they are the ones who check and confirm the incoming reports. But I can't really blame them either, since not everyone is aware of that "automatic expansion" thing and "It's not cloudy" is indeed a proper translation.
Piotr, those are two very different words. Esta (without accent) is the feminine form of este, and it's a demonstrative that means "this": "esta silla" - "this chair".
Está (with an accent on the 'a'; please note that all accents in Spanish go upwards) is a conjugated form of the verb estar. It's the present-tense él/ella form and translates as "he/she/it is".
- no está nublado - it is not cloudy
- esta mañana - this morning
I mistakenly wrote, "no estan nublando este manana". How many mistakes did I make? I count 4 or 5 mistakes. Duo didn't point out any mistakes. If you think Duo should point out mistakes, so we can learn from our mistakes, which is the premise behind Duolingo, please let Duo know.