In my understanding the seed is more sensitive than the master public key (though i might be wrong).

From what I understand the seed is the master key

seed -> hashing function = master key

More thinking on this point needed, for sure!

One more point, that i already put in the first draft of the guide, was that i noticed if you enter the same public key twice, electrum will let you know 'duplicate key' and prompt you for another one. That is, theres no need to stress about getting muddled up when copying and pasting keys, no harm can be done.

Neat!