From reading the different blog posts, and comments on them, and the Twitter debate which emerged from all that, it seems that three main conceptions of the Metaverse exists simultaneously :
1 - Some people consider the Metaverse to be directly related to a particular setting (Second Life, as the original one, or Opensim), in what we could call a "system-dependent" conception of the Metaverse if we would be speaking in biological terms. Or, if using a more correct terminology in terms of cyberpsychology, as a "platform-dependent" approach. The Metaverse is represented by the "best" platform at a given time, "best" meaning either the most popular, the most user-friendly, the most innovative. When the current platform gets outdated, for a reason or another, people would simply "move" to the next platform, hence, the "Metaverse" (being the sum and synergy of the people inhabiting it) would follow the transition.
2 - Some people consider the Metaverse to be much more than a single platform, but the interaction of multiple platforms over the Internet. The different platforms interacts with each others, and interact with the other facets of Internet, with the social media, and so on, forming what we could call a "Hyperverse".
3 - Finally, some people, like myself and Botgirl Questi for instance, seem to believe in a wider definition of Metaverse which would include both augmented reality, and, more important, would ultimately reach human body via implants, thus connecting the "network" to the "mind" (see previous comment), thus leading to the emergence of a true "Cyberverse".
Obviously, there is a hierarchical order in these three levels, one preceding the other. But saying that, I don't consider any level of interpretation to be inferior to the other. A lot of things can be understood about human behavior in virtual spaces with a single-setting "platform" approach, being a MMORPG like WoW (see for instance Guitton MJ (2010) Cross-modal compensation between name and visual aspect in socially active avatars. Computers in Human Behavior, 26:1772-1776 [PDF] ; Lortie CL, Guitton MJ (2011) Social organization in virtual settings depends on proximity to human visual aspect. Computers in Human Behavior, 27:1258-1261 [PDF] ), or an immersive virtual environment such as Second Life (Guitton MJ (2011) Immersive role of non-required social actions in virtual settings: the example of trade role-play in the Second Life Gorean community. Design Principles and Practices: an International Journal, 5:209-220 [PDF] ; Lomanowska AM, Guitton MJ (2012) Spatial proximity to others determines how humans inhabit virtual worlds. Computers in Human Behavior, 28 : 318-323 [PDF] ; Guitton MJ (2012) Living in the Hutt Space: Immersive Process in the Star Wars Role-Play community of Second Life. Computers in Human Behavior, 28:1681-1691 [PDF] ).
Even if more complex to investigate (at least for what is related to the experimental design), it is possible to touch the integrated "Hyperverse" level (for instance, when studying the co-existence of a Second Life role-play setting and a related and supporting blog, such as in Guitton MJ (2012) The immersive impact of meta-media in a virtual world. Computers in Human Behavior, 28 : 450-455 [PDF] ).
The idea of "Cyberverse" somehow echoes the concept of GUTE in AI (the "Grand United Theory of Everything", for a review of the history of concepts in Artificial Intelligence, see the excellent paper French RM (2000) The Turing test: The first 50 years. Trends Cogn Sci 4:115–122). And in a way similar to what AI-researchers are facing for the highest levels of integration, it is currently very difficult, not to say almost impossible experimentally speaking, to approach and study the Metaverse at the "Cyberverse" level, especially given the fact that the technologies are still far to be fully mature.
Still, technological advances are likely to make these three levels of interpretation merge de facto in a very near future.