I was beginning to think I was going crazy.
I can't comment on that. ;^)
I tried to modify 2 page styles in three different documents so that I could copy from one to the other without destroying the format.
Did you change the styles individually in the documents or did you use Load Styles... to copy the styles from other document files?
After several attempts, I was still getting a different format when I copied from one file to another. It turns out that if you don't save the document, the changes to the style are also not saved.
That's hardly surprising. Styles (modified ones, at least) are saved in document files. You must know that, as you say you are making similar changes in separate documents. You would not want changes to documents - including those to their styles - to be saved until you asked for them to be saved. So if you used Load Styles..., you will presumably be doing what that says: loading styles from the relevant (saved) document file, not any (unsaved) copy that might happen to be open in the application.
The odd part of this is that it is possible to close the file with no prompt for saving changes.
That suggestion *does* surprise me.
Now if I make a change to the text of a document, then try to close the file, I will get a prompt to either save or discard my changes, but I got no such prompt after changing styles with no change to the text.
Are you sure? Again, that suggestion surprises me.
Even more odd is that the "save" option is greyed out (inactive) unless a change has been made and it is not greyed out after changing a style even without changing text.
Since changing the styles in a document is changing the document (even without making any visible changes), both of these statements are exactly what I'd expect and don't seem at all "odd".
I trust this helps.
Brian Barker