I was ready to groan over all the complications of sorting out these rules and complaints .. and then saw this gem of a post. 
I simply read tomndebb’s note as being unclear whether omg was intending to call anyone a racist, or was sarcastically commenting on accusations of racism. Tom modded it as off-topic and inflammatory, since that’s what it was. It’s not Tom’s responsibility to clarify what rules might also apply if the statement had more context. Nothing about Tom’s mod note could be read as an invitation to call a specific poster a racist, although I suppose it could be read as an invitation to clarify an ironic use of the phrase “you must be a racist.”
But is that not exactly how we define personal insult: A negative remark about a poster as a person rather than the content of their posts? What then distinguishes between a remark being critical commentary or a personal insult?