Way back in history it seems that <xsl:message> produced just the message, but then some users asked for location information in the stylesheet of where the message was coming from.
Recently XALANJ-2340 asks us to remove that location information, perhaps with some option. So the questions for users are: How are you using <xsl:message>? Is it being run on a server, or web-server, and the output of xsl:message going to stderr and caught in a log and processed by other tools, or what? What would happen for you if we removed the location information? - Brian