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It's hidden behind the timestamp. Click the timestamp, get to the post information page, and finally click the flag link at the top.

The Flag link?

Why, what'd OP comment that required reporting?

Paraphrase is fine but I gotta know!

If you enable showdead in your preferences you can read the whole thing, which is a rambling off-topic comment on their product called "interference".

TIL about showdead - thanks!