On the Dutch Wikipedia, the message that is displayed when a filter triggers does not substitute $1 with the name of the filter when the text "$1" is included in a template on the relevant MediaWiki page. It does work when $1 is included on the MediaWiki page itself.
To reproduce this issue:
- Create a filter and add a custom message to it
- Have a page like https://nl.wikipedia.org/wiki/MediaWiki:Abusefilter-disallowed-kwaliteit as the message, containing {{Misbruikfilter-verhinderen-kwaliteit}}
- Have a template like https://nl.wikipedia.org/wiki/Sjabloon:Misbruikfilter-verhinderen-kwaliteit containing at least the text $1 or a template containing $1.
When the filter is triggered, $1 is not substituted with the filter name. In our case, the message "Het automatische controlesysteem heeft uw bewerking tegengehouden om de volgende reden: $1." is displayed like that. It should have displayed "Het automatische controlesysteem heeft uw bewerking tegengehouden om de volgende reden: Minimale kwaliteit." (per https://nl.wikipedia.org/wiki/Speciaal:Filter/104).
To see this bug "in the field", edit the Dutch Wikipedia as an anonymous user, create a new page and try to save the page with just the text "This edit does not meet the minimum quality rule and is blocked automatically."