Michael Brennan was among those arguing for clear labeling of parser capabilities. Certainly it does. For that matter, if you write a MinML parser, than call it a MinML parser and not an XML parser. If you do that, then you've got no argument from me. Gavin Thomas Nicol agreed, stating that users of profiled parsers cannot expect to be fully-interoperable with others .
Interoperability comes from standards conformance.
People that do not implement the standard should not claim to do so, and should not expect to be fully interoperable with people that do. In the end, deciding what subset of parser should be used for development is every bit as important as deciding what subset of XML should be used for DTD or Schema definition. It's the specific requirements of a particular application domain that will drive parser selection. For developers working on those platforms, a profiled parser might be the optimal choice. The same applies in situations where the XML being exchanged is rigorously controlled and regulated.