Ok, within an encounter, it takes a manouvre to change a talent socketed to a career (or party) sheet.
There is an interesting phrase in the rules for party sheets that go something like this "a player can use a manouvre to change a talent on the party sheet with one of the available talents of the ACTIVE player"
it specifically uses the term active player rather than "that" player.
Does this then mean, that for instance, if the active player (let's call him Bob) uses an action card that grants an ally (let's call him Dave) a free manouvre (such a card, i think, exists), that Dave can use that manouvre to change a talent on the party sheet for one of Bob's talents? If the above sentence is to be taken literally, then the answer is yes, isn't it?
Could Dave also use that manouvre to change a talent on the party sheet for one of his own talents? Again, in RAW, i think yes.
How are other people letting talent exchange on the party sheet happen? Even with all the above said, i think i might only allow players to swap talents on the party sheet with one of their own talents, unless the above sentence is clarified in the FAQ at some point...