Sometimes flags are applied to chat messages as a joke. This is a problem because every 10k rep user on the network then sees the flagged message and wastes time reading it until someone declines it. Similarly it is a problem when a flag is applied to an innocent chat message as an attack on the person.
Would it be useful to have an additional option when presented with a flagged message, to flag the flag itself as a problem? This would be separate from marking the flag as invalid, which could simply mean that the flagger has a different opinion on what should be considered offensive. The button to flag the flag would be only for cases where the flagger is believed to be deliberately abusing the flag system. This gives a way of detecting abuse without needing to divulge the identities of flaggers.
This button would be available to all 10k rep users (everyone who is involved in validating chat flags). What would be a clear unambiguous way of wording this?
It might also be worth considering where this additional flag should be sent. Direct to community managers, to site moderators, or to all 10k rep users for review?
Will it be a flag of the same type as a chat flag (and hence with the option of flagging it for abuse in the same way), or just a record in a database for SE to monitor over time?
If it's a flag that gets reviewed like any other, then if the flag abuse comes from a 10k user, that user should not be able to validate or invalidate the "flag flag". Presumably there is already a mechanism in place to prevent 10k users from reviewing flags on their own posts, so the same approach could be taken to prevent people reviewing flags on their own flags.