I want no XMP.
IPTC are well, only thesaurus exported is bad.
Maybe I'm not understanding the issue completely. What 'thesarus' are you speaking of? Photo Mechanic does not have a thesaurus.
Another point : I put for example famille | durand in keyword. I do that with Structured Keywords Panel, I don't write by myself, PM write itselft. when opening my IPTC with Atomic View, I obtain sometimes famille | durand and sometimes famille|durand without blanks.
I must use synonyme for properly work.
Why this inconstance ?
If you don't want to preserve the path of your Structured Keywords, you can turn it off. Then you'll just get a simple list of keywords like: famille, durand
I know nothing about Atomic View and have never used that software so I do not know what it does with IPTC information.
If you don't want to use XMP then at the very least, you're going to have to find out what character encoding Atomic View is using and force PM to use that same encoding when reading and writing IPTC.
XMP is the future of metadata. I strongly suggest that you adopt it in your workflow. IPTC is no longer being updated by the IPTC folks and no new fields are going to be added to it in the future.
-Kirk