When I was modifying my signature (updating it to a new one), it appears the following:
#BLOCK^_^DATA##BLOCKv_vDATA#. Anything I did incorrectly? It doesnt apper in my signature, but when I update my signature, in that instance, it appears a while (like about 0.75 seconds). This still have me curious.

this is the "secret" block data used for blocking members. if you don't want to see someone's post, hide sig or whatever, just click the Block member link to the left of each of their posts.

You can find out who blocks who by this but btw.