nope, just an insult.
ad hominem literally means "to the man," which is somewhat meaningless, so "ad hominem" and insult aren't really synonymous, though i do realize the phrase is short for the argumentum ad hominem fallacy. however, calling an insult an ad hominem (or even argumentum ad hominem) is actually an ad hominem fallacy fallacy, i.e., insults such as these are not even argumentum ad hominem fallacies. here's a good description of the whole thing.
now, some rewording and reorganizing to "you are wrong because you are an arrogant trolling sob," and it would have been an argumentum ad hominem.
taks
You are of course correct in what you write, I percieved T_Ns comment as trying to strengthen his position by accusing LoF of being a troll (a rationale for ignoring someone). Writing "ad hominem" instead of "argumentum ad hominem" and expecting everyone to understand is definitely something one could argue against, but it's nonetheless something I tend to do for some reason.