Handling multiple declarations of the same namespace in schematron

[raffazizzi]

Currently, multiple declarations of the same namespace in schematron are simply moved into the relaxng schema. This doesn't seem to cause an error, but the schema ends with redundant data. This was first noticed in this ancient issue: TEIC/TEI#941

[sydb]

Do multiple declarations of the same namespace in Schematron get moved into the .isosch file?

The previous ticket implied (well, stated, actually) that having 2+ of same namespace decl in the output was an error for ISO Schematron. If it is, neither SchXslt nor oXygen seems to care. Do we?