One of nice things with Diamine Majestic Blue is that you can dilute it with up to 50% water, and it still makes a very nice blue ink. That makes it, if it needs to be, 'safer' for your pen, as it is now half water.
Mind you, if the MB pens are so 'delicate' that they need 'special' ink, then I would have serious doubts about them.
While I don't have any, my understanding is that the Pelikan FPs are consistently wet, and so the consistently dry Pelikan inks (4001 & Edelstein) suit them well.
By coincidence I am looking at a TWSBI eco barrel stained blue by Diamine Majestic and some refilled cartridges that have been stained by Diamine Scarlet and Diamine Imperial Blue. I have tried cleaning the TWSBI, just will not budge, a blue stain between the piston and the section. I also have a Lamy Vista that is stained with Diamine Blue.
I agree on the dilution, in the past I have diluted the Imperial Blue to 80% water/20% ink, changes the color completely but it is quite appealing although the feathering is (even) worse.
With all due respect to previous posters, I only have two MB pens and it took me a long time to save up enough money to justify their purchase, for the sake of a small additional cost when buying ink I am not going to put anything in the pen apart from MB ink. I doubt that if my MB pens get stained or clogged that anyone who has given advice to use any other make is going to stand by their counsel and provide an indemnity for any loss of value, whereas I would expect MB to stand by their product.
Edited by smiffy20000, 03 December 2017 - 15:07.