"구름이 정말 아름답네!"

Translation: The clouds are really beautiful!

[LiKenun]

-네 is used to express surprise or wonder.

크네: (it’s) huge!

[LelLWH]

Very useful, thank you!

[Jeong-JinL]

So it's an extra "exclamation mark" that affects syllable count rather than statement intonation.

[JanThanDan]

감사하네

[JPark2000]

"The cloud is very beautiful" should also be correct.

[rkirsling]

Trying to line up Korean and Japanese sentence enders is amusing, hah. 네 is like よ (and not ね), 요 adds politeness (yet hearing ㄹ까요 sounds like a mild attack if your head is in Japanese mode). What fun. :P

[RaphalLefo1]

雲 は きれい だ よ。

[BUis2]

So there is the exclamation mark at the end of the sentence.

[Hoochy2]

'clouds are really beautiful' was not accepted

[cpLQ20]

'-네' is a declarative sentence

[brndtn]

the clouds sure are beautiful!