Tags not transferred to the duplicated photos

I agree with Greg_S.

I think that the real and only interesting question is which is your purpose to create purposely duplicates?

I can imagine special reasons to do that.

However:

1 - On practical as well as theoretical grounds it is considered to be a disaster to create duplicates when you can avoid them.

2 - There are other ways to create duplicates and even to include them in the current catalog. Either from the export as new files plus reimporting or the save as a copy or a version set with 'include in the organizer checked'.

So, choosing the 'duplicate' command must have a special purpose. Whatever that purpose, it must have other advantages than avoiding duplicating (using links to the same file). For me that means the ability to keep both 'versions' independent and able to be edited or used differently for different purposes.

As you have seen, the 'duplicate' command keeps the same tags, even if you don't 'write metadata to files'.

For people management, you can use either normal keywords and your own customized hierarchies (important for me for family and genealogy requirements), they are never lost in duplication.

You can also use face recognition  (totally useless for me) which implies a management by stacks. Stacks, albums and version sets are not attributes of a single file. They express relations between groups of photos. Duplicating a file does not in itself say which relation the 'duplicate' will have with other files.

There seems to be some inconsistency in behavior here.  I have tried the File>Duplicate command with several images.  With one that only had a People name tag, the tag metadata was not copied.  With another that had several keyword tags attached, the keywords were copied.  (I'm guessing that in this one, the metadata of the original file had been written to the file.)  If there is no metadata written to the file, using the File>Duplicate command copies the file into the catalog and appends "copy" to the name.  If metadata is written to the file, sometimes the file is copied to the catalog and sometimes it isn't.  And if it isn't, I can't import the file to the catalog because it is a duplicate of what is already there.  I have not yet figured out what may cause this discrepency. 

In any event, why do you want to create duplicates?  There are arguments going both ways as to why the tags should not be applied to the duplicate file.  I'm afraid what files the Organizer considers to be a duplicate remains a mystery to most of us.

What kind of tags are you looking for and where are you looking?  A duplicate file cannot be imported into the catalog because it already exists there.  If you look at the duplicate file's properties, in Windows Explorer, the tags should be present in the duplicate (at least if you have written the metadata to the original file).  I have just tested this with both keyword and People tags.  They all seem to be written to the duplicate file. I don't know what happens if you are working with a Mac OS.