Adressing someone without knowing their name

[magnusrygh1769]

こんにちは, マグナスです.

If you want to comment *your voice is amazing* to someone on youtube, but you don't know the name of the singer and wish to avoid saying *you*, can you simply say 声は素晴らしいです, or must i include *(namae)-san no, or anata/omae/kimi no*? Or just 素晴らしいです? How do i work around this in other similar situations, is there such a thing as a polite way to say 'you' in Japanese if it "cannot" be avoided?

Also, I noticed a lot of people using こんばんぬーん instead of こんばんは while watching a few Japanes gaming streams. Is こんばんぬーん formal or informal? Feminine, maskuline or neutral?

[LeesaJohnson]

I learned how to talk in the Japanese language, from this post. Thank you.