The words can't be used "interchangeably": as dojibear said, they have different meanings.I had this confusion whether the verbs are specifically used or can be used interchangeably.
This is one of the reasons I asked for the source of your sentence, and some context. If we knew this, and who said it, we could give you a more informed answer.This is what i was looking for! But could there be any specific reason as to why author chose to write it that way?
To me, "sharing" opinions suggests that some of the participants could well have the same opinion, with the result that some of the 'different' opinions will amount to being the same. On the other hand "exchanging" gossip conveys more of a sense of a two-way process of communication. You could reverse the verbs as "opinions are exchanged and gossip is shared" with relatively little difference in real meaning, but I think the collocations the author has chosen are more natural ones. You could even do it as, say. "opinions and gossip are shared". So really I think it amounts to a stylistic choice on the part of the author to compose a sentence which he thought sounded well-written.But could there be any specific reason as to why author chose to write it that way?