when u merge 2 threads, if the one that gets deleted has the latest post in the forum, there will be a link to this deleted thread in index.php after merging.. not a real bug but it should be fixed
if u didnt get it, here's an example: lets say that i post 2 threads now, thread A and then thread B.
If the 'base' thread is A, after u merge these threads, there will be a link in index.php (the 'last post' link i mean) to thread B, but it doesnt exists anymore