threads are moved for a number of reasons but primarily to keep the forums clean an organized.
and if a mod or admin decides it should be in the windows phone 8 forum, then thats where it goes... i wouldnt worry about it too much. just jump to the windows 8 thread for 7.8 info and topics.
edit* remember that these people volunteer a lot of their time, and work really hard to keep it nice, for all of us to play in. it is nothing personal when a thread is moved, although we sometimes feel that way. but rather an informed business decision, lol.