Yes sometimes the informant on a death record is confused or misinformed, so true. Doesn't seem like it's the naming pattern causing the problem with Elen's death record, which names her father as "John" instead of "Lars." Typically in the USA "Lars" would become Lawrence or Lewis or just stay Lars, but I've not seen it change to John. So it seems her grandfather was mistakenly named. That must have been tricky to sort out!
But yes, as you say, the Norwegian naming pattern throws descendants in the USA into a tailspin, despite that it is actually rather straightforward. Even those of us who have studied it still get tripped up because it is not a fit with our own mindset.
You wrote:
"My great (x4) maternal grandmother... was married in 1793 ... to Johannes Trondsen from the Instenæs farm. Thus the surname Instenæs in my maternal lineage."
To clarify: Norwegian women kept their own names after marriage. Your ancestor did not acquire her husband's name of Instenæs from him. She did not move it "into your maternal lineage" via marriage. So that statement is a little misleading, probably just due to hasty word choice. Perhaps you meant she acquired that address name by moving there after her marriage.
Again, "Thus the surname Instenæs in my maternal lineage."
Instenæs is not a surname; it is an address name. I think of a surname as a last name that stays with a person and follows him/her around. The address name does not.
First name + patronymic name (father's first name + son or datter) stay with a person for life, male or female.
Address name is not always used, and when it is, it is usually a farm. The address name changes depending on the address of the person. You can be Gene Hays Chicago or Gene Hays Seattle or Gene Hays Tokoyo but you are always Gene Hays.
In the USA and elsewhere abroad, Norwegian immigrants chose a permanent surname, which was necessary to assimilate. Some chose their patronymic name; some chose an address name. So often we hear "They changed their name at Ellis Island" or similar statements. Probably not true. The descendant is likely not recognizing the nature of the ancestor's name back home.
Here's a link for death of Arne Torjulssen, age 75, at Jaastad in 1847 - and thus born about 1772 (think this is Lars's father):
http://digitalarkivet.no/cgi-win/webcens.exe?slag=visbase&am...å = aa, as you know (Jårstad = Jaastad)
Kinsarvik is a subparrish under Ullensvang parrish in Hordaland - to explain the place name in the above record I posted.
Love the links - thank you!