I got my copy of this Diary in today's mail. The only additional information on the Peachtree fight is in the footnotes where they refer to the replacement of Johnston by Hood on July 17th (which can explain the aggression by the small Arkansas Brigade). A rumor of Johnston's return to command was circulated prior to the attack. Robert Dacus suspected an intentional deception to inspire a better effort. (Dacus, Reminiscenes). So, I read Dacus' terse paragraph of the fighting and he indicates that, indeed, Hood was pledged to defend Atlanta and was determined to drive the Feds back across Peachtree Creek. Reynolds drove them out of the first line of brestworks, but when the smoke cleared, there was a second line that they faced at sundown. They retired when it got dark.