&gt; That is a theoretically desirable technical property, but there is a strong argument to be made that extensibility, and the interoperability issues that result, is the Achilles heel of XMPP.<p>&gt; Of course, there is risk the other way around too: by over-specifying, you constrain your use cases, which may hurt adoption.<p>IMO anything that doesn&#x27;t have extensibility built in, will gain it after the fact whether you want it or not.<p>Better to have clear deliniation of duties and a standards body than a hodge-podge of uninteroperable things.