Redstone comparators do not test for valid power sources properly

1st BUD Placing a comparitor with a block behind it. Then an unpowered repeater going into the block anywhere. Placing a torch on any other side of the block. At this point placing a block on or to the one side left of the original block placed will cause the comparitor to update. break the block, place it again to cause the update to happen again.
2nd is place a block, place a lever on 1 side on the block. Place another lever next to block. Place dust from the back of the 2nd lever and connect it to the other lever. the dust will connect to the back and side of the second lever and run next to the first torch.
The 2nd lever needs to be on. place a comparator in front of the block. now anything that is placed next to dust that connects the levers will cause the comparator to update.

Edit by Zeb: Here is a video demonstrating the bug: https://youtu.be/y1Lza7M0RO0