[sic]As you know, "sic" is Latin and means, roughly, "exactly like this"; it is used to indicate that the funny spelling or grammar is the fault of the quoted, not the quoting, author.
For a long time it has also been used in less formal texts as the learned version of the exclamation mark, e.g.:
He claimed to have slept with 10,000 women [sic].Authors may also use it to signal that their standards are higher than other people's. Here's David Henderson quoting his commenter Pat:
Just because some immigrant wants more freedom than they [sic] have in their awful country doesn't mean they [sic] won't vote to make our system less free.A variant of this may be observed when Brits use "[sic]" to express their dislike of American English or vice versa, as in
The American stated that "the behavior [sic] of soccer [sic] fans certainly must reduce the market value of the Liverpool FC franchise [sic]."But even when used in the standard way, the use of "[sic]" when quoting contemporary texts has the side effect of drawing the attention to the fact that the quoted author made a mistake which the quoting author spotted.
I therefore suggest that "[sic]" not be used when it is obvious that the quote was inserted by means of copy & paste rather than typing up, because in this case it's bloody obvious that the mistake was the original author's. New technologies sometimes call for new norms.
(Added before publication: Having finished the text above I read through the comments at Henderson's post linked to above and found that commenter liberty had made pretty much the same point, which Henderson had conceded. Even so, worth making again. Especially since I've already written the post. These things don't write themselves, y'know?)