How to work for this solution？

[Di Zhang]

We can L1 L2 L3, L1 can't see any cases in L3 and L3 can't see any cases in L3. How to sync the comments from L1 to L3 and L3 to L1？ Is the setworkflow =false can avoid the before query？

[Mark Manders]

You really need to be more specific about your requirement.

Normally the L is set as level of where the Case is handled. How are you preventing them from seeing the Cases assigned to the level? Are you using Query BRs, deny-unless ACLs, or any other functionality? 

And it doesn't really make sense that comments are synced between levels, since it's the level of who is handling the Case, right? So you shouldn't have to sync anything, since L1 can't comment on L3 and vice versa.

And FYI: I think there's an error in your question: "L3 can't see any cases in L3".

Please elaborate on your use case.