@zogstrip Thank you for pointers, they seem to do the trick! I’ve made a PR 
https://github.com/discourse/discourse/pull/6518
I’ve tried adding some tests, but was generally super confused about how rspec works. They do seem to work though. 
One open questions: The search log still includes accents if the strip_diacritics function is called from Search.prepare_data. I am not sure that is the desired behaviour since there will be separate logs for queries that are identical from the search perspective.