I’ve found the database

checked my user tables modx_manager_users and modx_web_users. Both sets of users start at 1 and go up. So no negative id’s.
I’m back to the code:
It will only work for me that way. It only creates a createdby entry if the user is a webuser logged in via the front end. But when an entry is created the manager interface shows the user name of the equivilent manager user. Just to be clear if I use Ditto to look at these docs the user name shown in the [+author+] field is the manager users name from the modx_manager_users table.
To test further I created a new web user, logged in, created a new document. It shows up as being created by my manager user who has an id=5. In the modx_web_users table the new web user has an id of........5!!!
So I guess a workaround here is to create a web user for each manager user that needs to use newspublisher (for blogging) and make sure I match up the IDs. It will work but of course the slight pain is getting users to log into the front end for blogging and the back end for anthing else. Whilst I’m sure that this solution works in the sense of ’well, maybe thats how it should work...front to front back to back etc....’ I’m not sure I understand why a front end user would create documents as if they were back end users.
I hope I’ve got the terminology right here, wouldn’t want to offend anyone, but this split of front and back is how I see things.
If you have any other suggestions I could test I’d be happy to try if only from the viewpoint of understanding better.
Thanks for your help (and patience) so far BobRay.