I'd like to simultaneously thank you for the advice but also let you know that I did a trial-run anyway. I made a backup of the files, in that state and tested it out with the excess stuff stripped out. (it was all carriage returns, not tab characters)

What I was still dubious about was, about a page or two down from the data were two rows of three of those box-shaped non-characters (I'll use D's to illustrate)
----------

D D D

D D D

---------

but I chopped them anyway, along with the rest.

The campaign still loaded okay but, so far, I'm only interested in the heir names problem and never progressed more than about 1 full turn. I'd really need to let it autorun for half the day to confirm that no lurking problems remained.

So, a caveat for anyone else - my junk characters are not necessarily the same as yours and I was lucky... this time.

Backup what you have, chop out the suspect stuff, then test thouroughly.