Because mmcblk0p2 is the /home/ partition, and you can't unmount it. Running fsck on it while it is mounted(and it is always mounted when using maemo) is also, to put it bluntly: stupid. Of course, you maybe couldn't know, but the people who suggest such things should better do their research first, too.

If you want my honest opinion:

1. Reflash Rootfs and EMMC (as described here) (but backup at least your data first!)
2. Switch to CSSU stable
3. Ask yourself if you really need Power Kernel.
3. Start with a clean, solid system, don't install every crap and especially, don't listen to some random guys on this forum.

"But I don't want to lose my apps" - well, sometimes you want. Reflashing is the easiest way to get rid of all those problems and I have my reasons to recommend it.