I don't really mind the default being the answer. More often than not, the post I'm converting is one by the asker thanking the person who answered the question, so I move it to the actual answer. However, this might only be the case because I can see the admin, where a lot of these posts come from. For everyone else who can't see the admin, I definitely see how defaulting to the question would be more helpful, especially in the RMT section.
While I'm here, I might as well also bring up a related idea that could help fix something I've experienced personally. When an person converts and answer to a comment, it shows on the post that it was "edited" by that person. Multiple times I've had people ask me what I edited in their post, when all I did was move it to the appropriate spot. I thought it might be helpful if the "edited by" message said something more meaningful, perhaps "moved by" or "converted by".