http://checkstyle.sourceforge.net/config_filters.html#SuppressionXpathFilter does not state which XPath version is supported.

In PMD for example currently only XPath 1.0 is supported for violationSuppressXPath while for XPath based checks also 2.0 is supported.

The main problem with this is, that XPath 2.0 is not backwards compatible to XPath 1.0, for example "4" > "4.0" will be a numerical comparison in 1.0 but a string comparison in 2.0 and thus get different results, besides that it is nice to know that you can use more advanced constructs in your queries.