ok i should read some more documentation, I am sorry.
That's OK we all have to learn :)
But on the other hand i think that dpkg-reconfigure should say me if it wrote or not the configuration file to disk.
I think this only applies to this file and is as such a known 'bug' or 'feature' and there is a work around once you know about it ! I'm not sure anything is being done about this as Xfree86 is being dropped in favour of X.org in the new releases.
PAolo
WackojackoPS please reply to the list for the benefit of other users.