Re-enable forum commenting on a topic 24 hours after an admin has disabled them I would like an to have my Drupal forum set up so that an administrator can disable comments (by selecting disable comments in forum topic) for a particular topic, but then 24 hours later have comments opened up again automatically.

Can anyone help?
Your friend here is hook_cron().

Furthermore, you would need to check how to find the nodes that have had comments switched off in the last 24 hours. There's something useful you can check (perhaps it is the node's change time), or you have to keep a record yourself by implementing hook_nodeapi().