Hack: Automatically lock topics in Kunena

Sometimes you may want specific categories to have their topics automatically locked on first post.

Use cases include forum categories for classified ads. So the required behavior here would be to automatically lock a new "for sale" type topic, since for some reasons, e.g. forum rules and terms, you as the forum administrator, do not want replies to be public, but you require that the communication should only be done using personal messages.