MediaWiki 1.32.0-wmf.5 includes two changes which disallow some new characters in page titles:
- rMW6b8a5a137d3f: Strip soft hyphens (U+00AD) from title
- rMW7564624d1ca8: Strip Unicode 6.3.0 directional formatting characters from title
Existing pages with titles containing them will become inaccessible (except by page ID, e.g. https://en.wikipedia.org/?curid=8091). I don't know how many pages with directional formatting characters are out there, but for soft hyphens there were 2322 when I last checked (T121979#3923914).
Someone needs to run cleanupTitles.php to fix them. But please do a dry run first (php maintenance/cleanupTitles.php --dry-run) and post the results here. As far as I know the script is not run regularly, so there might be other broken titles in the database already (I think it's likely we have some broken due to Unicode normalization changes after we upgraded ICU recently). It would be good to know what we're dealing with first.
The script moves inaccessible pages to titles with the invalid characters removed, or if that is impossible (such page already exists, or title is still invalid), to page titles beginning with "Broken/". [It doesn't properly move them (with log entries etc.), it just updates some database fields, so there will be no on-wiki record of this having been done.] We should advise users to move them to proper titles afterwards (maybe in Tech News or separate announcement).