No one likes a doryphore – a pedantic & annoyingly persistent critic of others; a petty pedant, a person who complains about minor mistakes. The word comes to us through French, and is also the term used for the Colorado beetle – perhaps alluding to the meaning of the word related to “pest” (doing double duty for a bug and for someone who is a pest). Alas, I think doryphore deserves to be brought back – it’s much more sophisticated and subtle than mere pest.
Most languages in the world probably have a term for such people as they are, unfortunately, rife; in Swiss German we would say that someone is “bünzlig” – they’re usually the people who become meter readers and give you a parking ticket as you’re getting into your car 10 seconds too late. We recently paid a parking ticket because we parked for 10 minutes in a business parking, on a Saturday when the business was closed and spots were empty; yes, technically a ticket can be issued; but most authorities use common sense in such situations – but not the doryphore; they were likely waiting, watching for shoppers to do just that. In all the years I’ve been driving and parking in Switzerland, it’s the first time this has happened, but there will always be that one bünzlig person. Pity them. They live in shrinking worlds.
Stephanie Huesler 
Great word. I will think of you when I use it. 🙂