No sé quién irá a ver este video...
I don't know who will watch this video...
caption 11: Sevilla, España > Porteñas
How would we treat quién if Julia were to have made her statement positive?
As it turns out, an accent is still required, even though most English speakers would not consider this an indirect question. You might look at this as a case where an indirect question is present, but it is being answered. The highly respected María Moliner dictionary calls this type of usage aclaratoria (explanatory). Note that there is still no noun or pronoun present to which quién is referring, so it is not behaving as a relative pronoun.
Like other interrogative pronouns, quién also retains the tilde when used in exclamatory way. (You will notice that these "quién" exclamations don't translate to English literally.)
¡Quién pudiera tener tus ojos!
If I only had your eyes!
¡Quién te escuchara todas las bobadas que estás diciendo!
If only the rest of the world could hear all the stupid things you are saying!
So, are there cases where quien doesn't relate to a nearby noun or pronoun, but still doesn't take an accent? Yes, when the "who" refers to some non-specific person, and so is taking on the role of "indefinite pronoun."
Quien mucho habla, no tiene nada que decir.
The person/a person who speaks a lot has nothing to say.
In this same vein, the phrase como quien means "like a person who" or "like someone who," sometimes best translated into English with "as if he/she [were someone he/she is not]":
Él contestó el interrogatorio como quien nunca hubiera conocido a la víctima.
He answered the interrogation like someone who [as if he (was someone who)] never had met the victim.
And, in another "indefinite" role, quien can also be used in place of nadie que (nobody that / nobody who) in phrases like this one:
No hay quien me detenga.
There is not anybody who can stop me. / There is nobody who can stop me.
[In English we can't have the double negative]