grammar troll 

People who only reply to blog/news posts, to correct the grammar of other posters.

The grammar troll couldn't defend his side of the argument, all he could do was point out my incorrect "your/you're"

grammar troll by euromarkus August 16, 2011

Grammar Troll 

Often inaccurately defined as a Grammar Nazi (even here on the Urban Dictionary, see tags), a Grammar Troll is, most simply, someone who corrects the grammar of other people. Grammar Nazis may also correct grammar, but there are differences to be noted.

1) Grammar Trolls have no inhibition. They will correct all grammatical mistakes they see. Unlike a Grammar Nazi, they will correct trivial spelling a punctuation errors and nitpick word choice, especially when those minor errors or diction do not affect the meaning of the statement.

2) Grammar Trolls will do nothing but correct grammar. Most Grammar Trolls are aroused when finding themselves in arguments they realize they cannot win. That is when they resort to pettily correcting the most trivial mistakes, especially the misuse of homophones, in an attempt to undermine their opponents' credibility while not actually attempting to refute their opponents' points nor defend their own.

3) A Grammar Troll may use improper grammar while making these corrections and attacks. It is important to note that even true Grammar Nazis make mistakes. However, if while correcting someone a person makes a painful grammatical blunder that should not have been made, especially if multiple are made in succession, that person is a Grammar Troll.

4) Grammar Trolls are generally assholes. Generally, a Grammar Nazi will be respectful in correcting grammar. But a Grammar Troll is in almost all cases condescending, smug, and spiteful.

I had hoped he might give me a good argument, but he was only a Grammar Troll who gave up when I began proof-reading my comments.

Grammar Troll by tkdrocker806 December 26, 2014

Grammer Troll

Someone who feels the need to correct every little grammer error that they see to the point where it's just irritating and unnecessary.

Person A: Yo, peeps wat's happeninz?
Grammer Troll: *copies the last person's entire post and rewrites it* Yo, people what's happening?

Grammer Troll by Aldridge517 July 9, 2010