Let me do some load up thinking here
Ok, if you want to store your favorite threads in a special place, that only you could see:

First you'd need to make an extra table to the database. When a user submits a thread to his 'thread diposatory', a thread would be copied from the threads table to the new table, and tagged with the user's name (for retrieval)

Then when a users visits his thread collection, all the threads with the correct tag (username) would be selected.

It could be done with some mysql querys and a little hacking