Ssieth, I'm going to preface this with the full acknowledgement I have no idea how you scripted this, or what limits there may be. I really appreciate the script doing so much already!
I do have one request, though. Unless I'm mistaken, the only way to edit tags for a thread is to be in the thread and hit the bookmark button. Could there be another way, maybe from the bookmarks page itself? There are checkboxes already, so you can delete bookmarks, maybe you could use them somehow but add a button that just says "manage tags"? I only ask because I'm really fond of unread messages linking right to the message, but whenever you go and mess around with the bookmark, it seems like it reloads the thread so the unread marker gets lost. You can mark it unread again, but it'll send you to the original post/top of the page or something like that.