I guess perhaps I need to really understand more about the merging and the implications. Right now with all my testing etc I only have the Goodreads plugin enabled. And to be honest other than the odd small cover (but I usually manually replace covers anyway) I don't bother turning the others on in normal use anyways. As none of the other sources for my fiction books at least seem to offer much advantage.
So in the case of Amazon I'm not sure I would even have it enabled. As the Goodreads database consumes Amazon and Barnes & Noble and a few others. So provided I don't then there is no merge issue. I might have one of the others enabled but they won't have an ASIN or a goodreads id, so the merge of other identifiers wouldn't achieve anything. I think?
BTW, I am confused now about pubdate. My plugin is retrieving a specific value. But a different value is getting written into the edit metadata dialog. Are you doing some sort of pubdate lookup when you do your XISBN stuff or something?
I ask because one of the other features I liked about Goodreads was its "first published" date that I scrape and use. However I anticipated there are people out there who are very OCD about such things and want the date of their particular edition. So I put an option in my plugin to bring that back instead, and that is the date shown in the log, but a different (earlier) date is getting put into the record.
Is that a subtle secret addition you made to 0.8? In which case I will rip out my changes...