It does not really matter when a house was built and what codes, if any, applied at the time of construction: An unsafe guardrail is just as unsafe at a 100 year old home as it is at a new house.
As a home inspector in Bellingham, WA, I point out that codes are not retroactive but I, also, inform buyers of critical safety issues.
This is a guardrail, high upper deck at a two-story residence, and "part" of the rail is of sufficient height -- 36" over the surface of the deck. However, at another section of the same deck, as illustrated in the photo, the guardrail height changes and the rail is much too short to be considered safe.
A guardrail must be a minimum of 36" over the floor of the deck or any landing that is 30" or higher above grade. There are other problems at this high deck.
The spacing between the spindles at the rails is 6". That was commonly the way it was done several years ago. But, due to the number of injuries at decks, today, guardrails at locations 30" or higher require spindles spaced so any gaps are less than 4" -- to keep a child from passing through the openings. The other "practical" safety problem here, although it is not prohibited by code, is that the spindles are installed horizontally and that makes them climbable like a ladder.
Clients can, and will, do as they choose, as far as eliminating potential safety hazards at a house. From my standpoint, I will continue to report matters that I deem to be significant safety concerns. I do not want the moral responsibility of having said nothing, keeping mum just because a house was old, and then finding out that someone was later crippled or even worse.
A bad fall is a bad fall, maimed is maimed and dead is dead, no matter when a house was built. Taking the age of a house into consideration, as a primary factor, amounts to a pretty lame excuse for ignoring significant safety deficiencies.