"Yesterday I was nervous, since I was going to meet the king."
Translation:I går var jag nervös eftersom jag skulle träffa kungen.
eftersom is a conjunction that does not require the subject-verb inversion.
Check here: http://forum.wordreference.com/showthread.php?t=1879658
If found the explanation found in the linked source not very helpful. Is it because it is a compound sentence, where each verb phrase can stand on its own as a complete sentence?
Yes, that is correct. It works just like words such as och or men would here.
Is "i går" really correct? I would say "igår". In writing, it doesn't make a big difference but it does in saying.
Both are correct, but the Language Council (Språkrådet) recommends writing them apart, so we try to do that everywhere in the course.
Yeah, as a Swede I have always written "igår" and not "i går". Newspapers and dictionaries write "igår" too, I think Duolingo might have done a small mistake here.
Is that comma really necessary? Yesterday I was nervous, since I was going to meet the king
I believe in both Swedish and English it’s optional, but you put it there to show that the first part is a main clause and the second part a subordinate clause. In languages like German and Faroese, it’s mandatory with the comma there, and used to be in Swedish as well some 50 years ago.
The checker should ignore all punctuation. But it's been acting strange lately, picking on igår even though it's an accepted answer, for instance.
Would not "eftersom att jag..." be more correct? In speech it is ok to skip the "att", but I think that it should be there for correct, formal writing?
Other way around - there's not supposed to be an att there, but it can be used in colloquial speech. Especially among children.
I suppose that's arguable either way - is feeling nervous the same as being nervous? I'm leaning towards "nyaaaaaaaeeehh... maybe not", but I'm open to changing my mind if enough people disagree. :)