Steps to reproduce:

• Go to pl.wikipedia.org and focus the search box.
• Start typing "Bedusz".
• You will see results including "Będusz".
• Hit <return> to search for the plain Latin term.
• Your search results will not include local pages which include the non-Latin term.

On en.wikipedia.org for example, where ICU folding is enabled, the autocomplete and actual search return similar results which include the non-Latin matches.

It's likely that the search results will be fixed once we enable ICU folding using UTR#30 rules, but this autocomplete bit was mysterious enough to file as a separate bug.