We discovered in Wikisource that a search for kvibille doesn't produce hits for the older spelling qvibille (with Q instead of K).
Also, searches for jern and järn produce two non-overlapping result sets, where as a search for järnvåg produces hits for järnväg, so apparently å-ä are treated as similar (harmful!) while e-ä are not treated as similar (bad!).
The e-ä and q-k similarity is an issue in Wikisource, since these are old spelling reforms, but this is not an issue in the all-modern Wikipedia. Making e-ä and q-k match in Wikipedia too would most probably be harmless.
Is there any way we can change the behaviour? Per language and project? Or does it need to be changed in the Solr/Lucene distribution?
What is the current configuration and what sort of input is needed for an improvement? A short list of matching letters, or a full dictionary?