libxml2 (and thus XML::LibXML) has a hardcoded limit of 80 columns (old skool!) for its xml parsing errors, hence making it almost impossible to know the exact context of the error. 

e.g:
http://www.opensource.apple.com/darwinsource/WWDC2003/libxml2-3/libxml2/error.c
    /* search backwards for beginning-of-line maximum 80 characters */

I have a (sad) workaround in the validator for that issue, but ideally, libxml would fix it by either:
* having an option to output the whole list
* having an option (similar to $parser->line_numbers(1)) to output the column number too

The latter would be best, but either would do.

Recording this as a bug in the validator, so that we don't let the workaround sit forever.