I know that some people consider the presence of a leading underscore to imply that a variable is "private," that such privacy is a fiction, and assume this is why JSLint reports such names with an error message.
I use Google Analytics on a Web site I am building. I make reference to GA's variables, such as "_gaq."
I am trying to get my JS code to be 100% JSLint clean (I'm not religious about my coding style, and so will go with Mr. Crockford's counsel). That said, I can't do anything about Google's variables names... so, I guess I can't get 100% "clean."
I post here in case I've misunderstood the message, and can do something to comply with JSLint practices.
Ah, I've got this handled... I wrap the statements that use the underscore prefixed variables with JSLint commands to disable, then re-enable this class of error:
/*jslint nomen: true*/
... statement(s) with _var ...
/*jslint nomen: false*/