While the argument is very pertinant to people with newer cars running these fuels, I think the older IDI engines with purely mechanical injection are really not going to see any problems.

I've seem/felt every part of my fuel system in my hands (even the stuff inside the IP!) and after running varying blends of biodeisel (home made...nothing fancy at all) I see no problems.

The injection shop has tested my injectors, etc. and nothing abnormal has crept up.

In the long term? Perhaps a problem will show but honestly is gumming of something serious enough that it will physically damage the old clunky stuff?

Unlikely...

Newer cars? Yes I think there could be a problem.

Just wait and see...but don't worry about protecting your 1970's-1980's "delicate instruments"...they really aren't all that delicate