The "standard references" for questions about formal usage of most of the things [seriously] discussed here are the various "style manuals." Which one you should use depends on which industry you're writing for.

The manual for most commercially published (in the U.S.)reference and text books is the Chicago Manual of Style, University of Chicago Press, which I believe is now at the 14th edition.

Newspapers, and quite a few other "periodicals" generally follow the Associated Press Style Manual [I don't have a copy handy, so that's an approximate title]. The AP Manual uses quite a few style devices intended to produce very compact writing, and allows quite a lot of "slang" and "makespeak" language that would be rather annoying in more formal writing, but is perfectly appropriate in the target industries.

Many technical societies, who publish a whole lot of stuff have their own style manuals. If writing for one of them, it's absolutely necessary to refer to the specific information therein.

"Chicago" generally uses brackets "[]" for all editorial markings. Most things in brackets are in standard-roman typeface, but "sic" is an exception because of its frequent and traditional usage, and should properly be italicized in brackets [sic].

The "sic" notation merely means "as written," and carries no connotation that the quoted source is in error, although some people seem to interpret it that way. An obsolete "comment" was the italic "!" (without brackets) which was intended to convey the editor's disapproval of something quoted. This usage is severely disparaged in modern usage. The ! notation is considered a "dumb-ass" comment that carries no meaning for a reader (except that the editor is a dumb-ass?). The quote should be simply marked with the standard [sic], and a separate [this is a stupid error by the author] - or something similar that clearly states the editors objection should be separately inserted.

There are any number of "generic" style manuals that discuss common errors of usage and that explain less common markings and abbreviations. While these are sometimes excellent, they frequently don't give a very good sense of intended audience, or of differences (say between U.S. and British usage) for different audiences. Given the caution one must use in choosing an appropriate one, they're still much better than relying on dictionary definitions for advice on usage in print.

John