- Correlation is not causation: the few readers who don't know this already won't benefit from mentioning it. If there's some specific reason you think a a study is wrong, describe it.
- "If you're not paying for it, you're the product" - That was insightful the first time, but doesn't need to be posted about every free website.
- Explaining a company's actions by "the legal duty to maximize shareholder value" - Since this can be used to explain any action by a company, it explains nothing. Not to mention the validity of the statement is controversial.
-  - This isn't Wikipedia, so skip the passive-aggressive comments. If you think something's wrong, explain why.
- Premature optimization - labeling every optimization with this vaguely Freudian phrase doesn't make you the next Knuth. Calling every abstraction a leaky abstraction isn't useful either.
- Dunning-Kruger effect - an overused explanation and criticism.
- Betteridge's law of headlines - this comment doesn't need to appear every time a title ends in a question mark.
- A link to a logical fallacy, such as ad hominem or more pretentiously tu quoque - this isn't a debate team and you don't score points for this.
- "Cue the ...", "FTFY", "This.", "+1", "Sigh", "Meh", and other generic internet comments are just annoying.
- The plural of anecdote is not data
- Cargo cult
- Comments starting with "No." "Wrong." or "False."
- Just use bootstrap / heroku / nodejs / Haskell / Arduino.
- "How [or Why] did this make the front page of HN?" followed by http://ycombinator.com/newsguidelines.html
What comments bother you the most?
Amusing note: when I saw the comments below, I almost started deleting them thinking "These are the stupidest comments I've seen in a long time". Then I realized I'd asked for them :-)