[[OSM:Notifier.signup confirm html.user wiki page/en]]

If you actually open the category, you can see that it has no members. The hook does not prevent displaying the category information on page preview/after save. Perhaps setting content model to text for translations would do that too.

We could do that, but it would mean not parsing any wikitext, right? It seems excessive, the bug is fixed and some difference between the parsing here on TWN and in the target destination of the message is unavoidable.