Another vote for #1383132. I've been able to distribute checks to my students using an absolute pathname for the location of the standard suppressions file, but if it's a Windows pathname, my Mac chokes on it, and vice versa.
If you don't want to mess up the DTD, it could look like:
<property literal="<suppress files=\\" Test.*.java\\"="" checks="\\"MagicNumber\\"/"><suppress other-rules-go-here=""/>"/>
This is a little more error-prone and harder to use than the more user-obvious
<suppress files="Test.*.java" checks="MagicNumber"/>
In fact, it would be neat if SuppressionFilter allowed BOTH a "file" property and an arbitrary number of <suppress> tags; that way a whole site could have a baseline suppression filter file, and individual users or projects could add other suppression filters to it. Even better would be to allow multiple files as well, of course...