I think D3 does it right. Companions will have cool little things to say here and there and at least when they say something in battle its relevant to their or your situation instead of random crap.
Find the companion comment files and viciously delete them.
It might be a good idea to then replace them with placeholder files so it doesn't bork over missing files.
It might be a good idea to then replace them with placeholder files so it doesn't bork over missing files.