The bug

Once you execute /gamerule maxCommandChainLength 0 in a world, you will never be able to execute commands in that world again unless you modify maxCommandChainLength directly using an external world editor.
While this behavior might be intentional and/or could sometimes be useful, there is also the risk that a typo or wrong arguments can easily cause commands to never be executed again in the current world. In particular, on a dedicated server, you cannot even terminate the server with /stop.

How to reproduce

1. /gamerule maxCommandChainLength 0

   → Gamerule maxCommandChainLength is now set to: 0

2. /gamerule maxCommandChainLength 10000

   → Command execution stopped due to limit (executed 0 commands)
   No more commands can be executed in this world.