Oh, interesting. (2) and (3) are nearly identical - I wonder if we are over complicating things by having different texts for these two cases.
For now, looks like we can just create a new string for illegal and make sure it works, eg
responder:
illegal: "The post was flagged as **illegal**: the community thinks it might be breaking the law."
We could also create a new string in (2) and (3) to cover all the custom flags, eg
flag_reasons:
custom: "Your post was flagged as **reason**.
responder:
custom: "The post was flagged as **reason**.