What thread are you talking about?
Threads are only merged for 2 reasons:
1. After an MMA event, the staff marks a thread "****all discussion of this topic goes here*******", and in that thread there is a note that says any threads other than this one will be merged.
2. Threads on the same subject, like if two threads were made about why Nog is an awesome guy, those two threads could be merged into 1, as it's the same general topic.
If a thread gets merged and you are unsure why, you can always PM someone on staff and ask, and you will be told why it was merged.