Loremaster and Lucky Charm might be acceptable to stack party-wide, since they're basically 'knowledge' skills, and it can be handwaved away as everyone knowing exactly the right amount of different things.
Barter and Persuasion should absolutely not, since even in SP you can approach certain dialogues/shopkeepers differently if you use a different character, and it would make no sense to have everyone involved in conversations that, for example, are meant to exclude them.
