Yep, I quoted it upthread. In that post I also pointed to the other passage in the PHB that refers to PC personality, namely, the discussion of morale. (Which explains that PCs don't check morale, because the player chooses whether they are of cowardly or brave personality.)In the interest of contributing to the collection of thoughts about D&D in the 70s, although it is admittedly not Gygax, here is Mike Carr in the Foreword to the AD&D PHB (one of a list of "guidelines ... to make the game experience more fun for everyone concerned...")
"Get in the spirit of the game, and use your persona to play with a special personality all its own. Interact with the other player characters and non-player characters to give the game campaign a unique flavor and "life"." (2 June 1978)
FWIW
I don't think these two passages are comparable, in scope and even intent, to the 2nd ed PHB.
I think that, in 1978, it was taken for granted that you would have a name for your character, and might have some basic tendencies. But the full ramifications hadn't been thought through, at least in print and in the published guidelines.
For instance, suppose you decide that your character always attacks goblins on sight, because she hates them so much. How is that meant to interact with the advice about always casing the dungeon before staging a treasure-recovery raid? Or with the advice about avoiding wandering monsters unless it's impossible to do so?
The guidelines are silent. The XP rules are silent - they explicate "good roleplaying" simply by reference to class function and alignment. And speaking of the latter, does a character who has LG written on her sheet, but who sees some goblins and therefore attacks them (because she is someone who attacks goblins on sight), thereby jeopardising the wellbeing of her friends, lose her LG alignment?
The original AD&D rulebooks, and Moldvay Basic, simply don't provide any guidance for answering these questions.
The guidance in the 2nd ed books is, on the whole, no better - it basically tells the GM that s/he is to sort it all out some way or another - but I think they were at least conscious of the issues.
This is not a criticism of Gygax's rulebooks. Rather, it's an observation about them - they don't in any serious way engage with the proposition that the aim of playing the game is to cultivate a unique personality for one's PC. I think those writers simply saw that as a byproduct of what (to them) was the real deal - namely, beating a dungeon via skilled play.