Actually, it's not so much "non-standard" as it is an obsolete standard. Moot difference, I admit. Either way, Microsoft could break it. Not like they have a history of doing that...
As a developer myself, I've had to deal with Microsoft's whims for many years. When Windows breaks my code, it's up to me to fix it. Sometimes that's been a royal pain. My application also interfaces with Word and Excel, and my code is littered with "if Word version X, do this, else if version XX, do that".
What MS calls "standards" are actually a moving target. Even following the rules as dictated by MS is no guarantee they won't break your code, even in a fix release (excuse me, "service pack"). In the end, it's up to the application developer to stay on top of MS (and Apple's) capricious ways. Melda is one developer I'd trust to quickly address any future incompatibilities.