Perhaps, but if you quote both people explicitly in the post – which we encourage – it should be quite clear.
The case of clicking the reply button on a particular post and then selectively quoting just one other person in your reply seems rather cherry picked to me. That’s quite unusual.
I think the major loss would be that every single reply would suddenly have this weird metadata shoved into the body, when the reality is that 95% of replies are to a single person – or to nobody at all, because they are replying to the topic in general.
You’re proposing a change that would make it worse for the 95% to make the 5% case better. That doesn’t wash.