Was going to leave this as a comment, but it's more of a secondary answer.
I would only bring it up here if you're flagging multiple times and not getting any results, e.g. the behavior is continuing without a moderator intervening. And even then I would only bring it up as a general question ...
"why are my repeated offensive comment flags not resulting in action?"
... never by naming specific users.
We like to address behaviors here, not specific users. It's more useful to more people that way, and it's more optimistic: people's behaviors can change. Addressing the behavior decouples it from the person and removes any blame or stigma that might work against positive change in behavior.