Our standout source of merge conflicts at the moment is on preferred language. We are no longer seeing these where the language is fundamentally the same (en vs en_US vs en_AU vs en_NO) but we are when the language has changed.

In brief discussions previously there was some consensus that we should go with last donation - even thought it seems likely that if they use Japanese & then English they prefer Japanese but got landed an English form it seems too unreliable for a rule.

I did have some concern that this could make it harder to deal with the situation where there was a name mismatch due to language change. Specifically I have seen a number of Japanese duplicates where they use a name in Japanese writing to go with their Japanese donation and a name in English to go with the English donation. However, in those cases there would also be a conflict on first name & last name so they would not merge. I think there may be some complicated multiple match situation where losing the language conflict on the first merge would reduce the information available to a later merge but it's not feeling like a case for not going with the most recent donated language

Change 318224 had a related patch set uploaded (by Eileen):
Adjust preferred_language dedupe conflict resolution to prefer later donor.

https://gerrit.wikimedia.org/r/318224

Change 318224 merged by jenkins-bot:
Adjust preferred_language dedupe conflict resolution to prefer later donor.

https://gerrit.wikimedia.org/r/318224