Hey Greg, I don't think conversations can be merged -- just deleted. And I don't think we want to lose the conversations that have happened on either thread.
Just FYI, lead-to-account matching will most likely be supported in Marketo as a standard functionality in upcoming releases in 2016. ABM is a one of the focused topic of 2016 product roadmap.
Pl. feel free to reach out to me directly on mjeswani@marketo.com for more details on this topic or any other ABM topic.
I would suggest to also create an IDEA on this topic. This helps in prioritization of the feature.
Thanks,
MJ
Product Management