Louise Brooks on Joan, in a 1957 unpublished essay originally intended for an ultimately unpublished book by Brooks called Women in Film, about some of her contemporaries:

...How delightful it was then to see the front door pop open and to watch [director] Eddie Goulding come bounding across the room like an enthusiastic lion about to eat us up… 

He had just finished directing Sally, Irene and Mary. It was a big hit but he didn’t talk about that, nor did he talk about Constance Bennett and Sally O’Neil who were also big hits in the picture. He talked exclusively about Joan Crawford. “She’s the find of the year, Walter – the greatest find of the year! Beautiful, wonderful emotional quality – bound for stardom.” 

What a crust of jealousy those words imposed on my naturally sulky puss. Nobody ever talked that way about me. Walter [Wanger], when he looked at the rushes in the projection room, actually laughed at my acting… As I listened to Eddie rave on about Joan Crawford, it seemed to me that he had dropped my movie career awfully easy… That Joan Crawford must be really something! 

The first chance I got, I went to see Sally, Irene and Mary. She was beautiful, all right, in spite of her hair parted in the middle to give her a madonna look. And her legs were beautiful even though she used them to dance the Charleston like a lady wrestler. But she played her part like a chocolate-covered cherry – hard outside, and breaking up all gooey with a sticky center. I didn’t care for her… She isn’t truly like a chocolate-covered cherry; she is like biting into a delectable piece of wedding cake and hitting the brass ring.

To me Joan Crawford’s screen portrayals are all one: a series of transparencies through which she projects her daydream – herself – a wonderful abused kid. On the screen every ladylike effort is stretched by the memory of self-abasement; the salt of every tear is the salt of self-pity. 

…Leading a life in triplex – the person she was, the person she thought she was and the screen person – she played [her roles] like Joan Crawford imagining herself to be Gloria Vanderbilt playing the part of a poor, kicked-around whore. To be a movie star and not approve of her private self; to feel that Hollywood does not, and the public would not, approve of her private self, makes for a deadly state of confusion…

Like every young girl in pictures, Crawford also must have been influenced in her personal life by that movie concoction called a “sympathetic” starring part. For sex and box office, the heroine is made to look as bad as possible through most of the picture but done up in the end like an organdy apron as a sop to the American myth of womanhood… 

As for Crawford’s Flaemmchen [the stenographer who sells herself to a rich man] in Grand Hotel and her Sadie Thompson in Rain, they are utterly consumed by her pity. The fate-worse-than-death treatment given the trollop role by the highly emotional actress has always been a wonder to me anyhow. Not that I advocate making a life of shame enticing, but to be so widespread both in reality and on the screen it must bear some mask of attractiveness. 

I once knew a real Flaemmchen [Jane Kent] in New York, and if she ever felt sorry for herself, it was because she missed getting some deserved adornment, not because she wasn’t a good girl getting varicose veins behind the counter in the 10-cent store. Through her boyfriend, a bellboy at the Waldorf Astoria, she met and made herself agreeable to a variety of gentlemen ranging from Texas politicians to Hindu princes. In a simple grey suit with her golden curls piled high on the top of her head, done up for a weekend with one of these men, nothing could have been farther from her spirit of delight than Joan Crawford’s gloomy preparations in Grand Hotel to go away with Wallace Beery. In his place, grown uneasy under her accusing eye, I should have sent her off to the nearest Christian Science Reading Room.

Thanks to Michael H. for sending in Brooks' essay.