@grantshoarma - when every single thing is identical - yes it would be possible to arbitrarily decide to delete one of them. However in my opinion that is just two small a scenario to try to code for. Remember it only takes one tiny detail to *not* make them identical (an extra format, or the slightest variation on the title/author/series/cover/description/published date/...).
For most users coming to this plugin they have been using calibre for a long time. Which means they have a large database of books, which they have been working on. Likely over that time period they learnt far more about using calibre, downloaded other metadata plugins, cleaned up some books, changed various settings about how their files were imported, etc, etc. So the likelihood that they have two identical versions of a format isolated in non-touched rows is absolutely minimal (remember calibre would have warned them about duplicates if the titles were identical!).
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