Cool Charles, only fair that since you suggested the improvement you get some benefit out of it
There is one more scenario that this plugin will not catch and I don't know whether to try to cater for it. That is where the authors have the names in a different order but not swapped with comma. So you have A B and B, A will match. but A B and B A will not, nor will A, B with B, A.
You could find duplicate books using an ignore author search so that is fine if you do have a duplicate title. However a user might argue that an author duplicate based search should find this.
How often does it happen. Probably more than it should. I think the option of swapping names when adding authors is partly at fault, as if you have that selected it can give unintended results. It is once again that old chestnut of no setting for commas in a display name. So if I have a file with the name A B for author, and swap names checked, then I get the author B A rather than B, A. I think it could have it's logic tweaked to say if no comma when swapping then add one in and vice versa. However that might upset people who for some reason had the names stored without a comma the wrong way around and not want commas in the display name. How prevalent that is I do not know?
Now if the user downloads metadata and has overwrite author ticked, then the name gets fixed so the problem should go away. However there is still the issue for a lot of legacy books or where the user decides not to download metadata.
So... Is it something I should try to cater for? I think it should just be in the author duplicate (ignore title) searches if we do. There is the minor thing of it creating more false positives, such as two authors whose names when flipped happen to match but hopefully that is relatively rare and easily exempted.
EDIT: I'm going to dispute my own suggestion here (I do talk to myself a lot). I think that differentiating between title vs author searches is wrong, they should both have this check. The question should be just whether identical author searches should have it or not. Which I think the correct answer is no. It means more code twiddling on my part but hopefully a more consistent result so you can get A B / B,A / B A and A,B all in the same group.