I'm optimistic the existing system works: merged answers need not lose their distinctness

Proposal no. 2 would be great, and some version of it would be very helpful even within the existing system as a way of auto-suggesting to people that an answer should be merged.

In the existing system it possibly to merge an answer with an existing answer while still keep a sense of their separateness. For example, two users MrAndrews and MsBlue could have two separate answers within the same answer simply by adding "[username] says:" before their bit. Like this:

MrAndrews says: Yes, that's a very goood idea

MsBlue says: Yes, I also think that's a good idea. My grandma did the same thing and it worked wonders for her.