No, it's not marketing as such. The short story is that they are permanent, but also somewhat corrosive, and they clog easier than many other inks. So they're not for every pen, or for everyone.Is 'iron gall' some kind of special ink, or just a marketing name thing? I've seen this phrase on some other inks when I was browsing Goulet Pens the other day.
I should never have sold my 342 OM!Montblanc 342 with a medium, right oblique nib and Montblanc Royal Blue ink
Montblanc 342 with a medium, right oblique nib and Montblanc Royal Blue ink