Questions about NPN and being "holder in due course"

[Eric M.]

Despite being a part time hard money lender I am afraid I know little about buying and selling existing notes and it is an area I am curious about. I have been reading Lorelei's Legal Lessons which though it is 15 years old, was recommended by others here.
I have been learning some interesting things.

I am most confused with the section about buying delinquent notes. While she doesn't say stay away completely, she warns about the dangers of not legally being recognized as the holder of the note. This seems to be a major drawback of buying NPN's but this belies the fact that NPN investing seems to be all the rage.

Is what she says true? If so, how does this fact about not being the holder affect you when you purchase an NPN from an originator and then try to foreclose (or demand payment in any other way)? I know the "foreclosure help" people often tout demanding proof that the foreclosing lender is the holder of the note in court to delay or stall the FC process.
Seems like it could be a killer.

Any experience here?