"yIjaH 'ej yIyemqa'Qo'!"
Translation:Go forth, and sin no more!
Yes, this is definitely being said to only one person in this sentence. As you have speculated, you can know that because of the yI- prefix. Actually the first part yIjaH could be addressed to multiple people and mean "go to him/her/it." But I don't think yem can take an object, so the second part could ONLY be said to one person.
Ah, okay, that makes sense. Just so I'm certain, if yIjaH were referring to multiple people in this sentence, would we then also know that there has to be an object? Or can we use yI- with any verb that can take an object, regardless of whether it does in a given sentence? Thanks so much as always!
The first is true, the second is not.
If there is an object and you use yI- you could be speaking to multiple people or just one. All imperative prefixes that indicate ANY object are the same regardless of how many people you are commanding. The only time the prefix changes for number of people being commanded is when there is no object.
So when you encounter pe- you know it's to multiple people and there is no object (with the important note that there could be a reflexive -'egh or -chuq which are sort of objects).
If you encounter yI-, then you have to figure out how many people are being spoken to or if there's an object. If the speaker is talking to multiple people, then there must be an object (otherwise the speaker would have said pe-). Or if there is a clear object, then you know the speaker could be addressing any number of people.
If I say, yISop, you cannot tell if I mean "Eat!" or "Eat it!" If I am talking to multiple people then I must mean "Eat it!" because the command to multiple people to eat (in general and not something specific) would be peSop!