Hey Starson17, sounds like you had a pretty positive experience which is great to hear. I am sure you will like the next version even more with making that search restriction/highlighting/sort stuff all happen automatically.
It is an interesting comment about automerge. For myself I would be sad to see it removed completely. I've never been a fan of the "match on title only" default implementation so to have to go back to that would be a step backwards imho.
Re Copy to Library. What would worry me about automerge with this would be the situation of doing "copy and delete", then find that actually it never made it to the destination because of an automerge setting. I don't have an immensely strong opinion on it because I can't see myself being in a scenario of using it I'm afraid. I use Copy to Library a lot but I am migrating unique sets of books author by author so unless I screwed up by independently adding a book to my newer target library I won't hit that situation.
As for the algorithms, that's another interesting question. I can see why you are bringing this up
. For myself, I like the fairly conservative approach that automerge takes, and know that "worst case" I will end up with some "duplicates" from a slight variation of author name or whatever. So I don't think you would want to offer "Similar Name, Similar Author" as an option in case it was a bit too aggressive? At least once this functionality is put into Calibre as a user you will know that at any time you can periodically check to see what duplicates you have (or do so after adding a bunch of new books).
For new formats of a book, having automerge automatically sort that out for me is brilliant and I don't want to lose that. For duplicate formats of a book, that is where (personally) I will be wanting to be creating new book records and manually reviewing by comparing the EPUBs side by side or whatever before making my merge decision. I think even if you made no changes to automerge it does everything I would like from it, but that is just my opinion/needs of course