"I used Grammarly to grammar check this post, because I don't want any nit-pickers finding errors in it.
It's always amazing how some of the worst readers, those who can't spell I, can find errors in books. Although such criticism can be instructive, it's often nitpicking.
The source of the phrase is gross. It comes from the task of removing eggs of lice from someone's hair and clothing, a tedious job that requires close attention to detail. It's interesting to note that fifty percent of Civil War soldiers had lice, so one of their favorite pastimes was having lice races.
Maybe that's what some readers are trying to prove--that they can find flaws in an author's writing, even though they themselves can't write a complete sentence. Such fault finders never seem to make any suggestions for improvement, either. Perhaps their goal is just to win the lice race by finding the most errors.
Should authors listen to them? I'd say Yes. It's possible to learn something from anybody. However, don't be discouraged because your writing isn't perfect. You should also make your own final judgment regarding whether the criticism is justified with an eye to considering the source. Remember, monkeys nitpick all the time.