On facebook, I've used the "Angry" icon sometimes to say "I agree with what the poster said, and it makes me angry also".
(Likewise with the "Sad" icon).
I've mistakenly used the "Verbose" icon when I intended "Applause" and my aim was off. When I've done that, the posters have written politely and inquired if it was intentional, and I've immediate repaired my error.
I do have to say that I'm a little confused about the distinction between "Ad hominem" and "insulting" ...