But what is getting personal? Other than the use of the word "person", there is no actual reference to anyone's person.

The personal aspect would be bad, except it doesn't exist.

The tropiness of the phrase I'll take your word for, as I don't frequent any other online discussion sites. It certainly doesn't add to the discussion.

Is a phrase that is extraneous, currently popular/cliche, and merely possibly offensive because it's typically used ad-hominem elsewhere, really cause for threatening to ban a user?

I think you're over-reacting.