"Doh!" is a minimalist emotional response that allows its poster to succinctly express his impression and thoughts on the subject posted. It just happens that this impression is conveniently described in just 4 letter glyphs.
On the other hand your comment doesn't add any meaningful contribution to the discussion, nor does it bring any new meta-discussion subject to the table. So please keep such comments off HN, especially when they are directed at someone with 500+ karma.