Hello,
I noticed a very strange bug for repeating command block.
Indeed, we can powered a repeating command block by an other command block and not by redstone.

For execute that, place one repeating command block (/say 1) next to an other command block (any of them - I used an other repeating command block - /say 2)
http://prntscr.com/921o43

Powered then the two command blocks
http://prntscr.com/921ou5
This written many "1" and "2" for us example.

Next, remove the redstone_block who power the repeating command block (/say 1)
http://prntscr.com/921quf
What? We see "1" in the chat .. But the repeating command block is not powered .. Is it possible? Is it the second redstone block who power the repeating command block (/say 1)?

No, because if we remove the second redstone block :
http://prntscr.com/921rsg
The "2" from the second command block disappears. But the "1" is always here ._.

The "1" disappears only when we removed the second command block.
http://prntscr.com/921sjh

This bug works with all types of command blocks for /say 2.
http://prntscr.com/921t2a
http://prntscr.com/921tfo

So, the second command block (/say 2) power the repeating command block (/say 1) if we remove the redstone block of the repeating command block in first :/
It's a big problem because we can't place repeating command block next to others command blocks :/