It derives from an expression deep in the history of Usenet or e-mail (hyphenated), when hapless newbies (two syllables) were told by harried sysops to RTFM, read the f* manual.
And while it is being used now to simply reference the article, RTFA was originally used in the same way as RTFM. A way of expressing frustration to a commenter who should have read the fucking article first.
A way of referencing the article that has been submitted and these comments are discussing.