I came across this on Twitter, it seems to be mostly a question but sometimes an exclamation. Is it とは, or maybe とか? How do you use it? My dictionary has a とな as word that come at the end of a sentence to get confirmation. Is this the same?
画像も貼らずにスレたてとな？
今日は次第に雨とな。
千葉東方沖震度4とな？
むっちゃんがイケメン店員とな(￣□￣)!?
The avatars of people using it are overwhelmingly cute. Is this a cute word.
とな is basically formed by combination of と and な.
You may use ～とな at the end of the sentenses like that, basically use when you heard it from somewhere else and also express your agreement when you repeat that. It has similar meaning with ～というのだね.
You may also use ～とな at the end of the phrase (even in the middle of sentence), and it express light emphasis for your agreement.
ref:
As YOU wrote, とな in these examples is a combination of the particle と signifying quotation and the particle な signifies that the speaker wants reply or agreement or wants to make sure. I think that とな in this meaning is rare in the modern Japanese except as an Internet slang or possibly in some dialects.
“画像も貼らずにスレ立てとな!?” is a set phrase used in some Internet forums including 2channel. It means something similar to “You started a new thread (in the forum) without even including a single image in it? Seriously?” I guess that many of the uses of “とな!?” (or “とな?”) are inspired by this set phrase.
