As others have said, these are perfectly acceptable expressions in Irish. If you watch Ros na Rún, you will occasionally hear sentences like this. The reason why these are written with a question mark rather than a period is to express the rising intonation that marks the speaker is surprised or is unsure but hopes the statement is true. For something like
Níl sé an-tinn? you would hear this in the recording which really helps give better context to what's going on. This sort of nuance is an aspect of spoken language that is very difficult to convey in writing.
If you think about this in English, you'd probably never ask someone, "Is he very sick?" not because of grammar but because it's almost kind of rude. Usually you'd say something we consider a bit more polite like, "Well, I hope he isn't too sick?" with a rising intonation to show we expect an answer from the person to whom we are speaking that will confirm our statement.
I want to go a bit further on this point and say that people have certain notions of how they speak a language and how a language should be spoken and that very frequently the way they actually speak the language or the way it is actually spoken is far more flexible and nuanced than their perceived opinions would allow. Once I had a discussion with a well educated person about "standard English" and expressed my opinion that educated, middle class Americans do not speak standard English to the degree that they actually think they speak it (
circa 1996, to give some context). She, however, thought that she spoke English very much the way she wrote it and couldn't even understand how I could take such a stance. My reply was, "Well, 5 minutes ago you just asked Jim, 'Where's my keys,' but you'd never allow a verb to disagree with the subject like that in writing."
My point is that, while there are certainly things that are clearly ungrammatical, making categorical claims about a living spoken language can be a really sticky thing to do and it's far too easy for people to disparage others based on an opinion that is itself not necessarily correct.