Just to double check, I replaced the htaccess file I have with what you linked. Same results: thread.php?test as the url. If I manually input domain.com/test, as it should be, I get a Multiple Choices error, and it suggest test.rss as the link.
My htaccess additions are:
“RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]ErrorDocument 404 /404.html”
While not edited, I replaced the functions and start files as well. Same results.
Edits I have made have been to html files.
Hosting is with 1&1, well whatever they changed there name to now. Linux Professional shared package.