"Homely," Clumsily Theological, Candid
Yeah, it's a little awkward to talk about Margery Kempe's "writing style," because, strictly speaking, she's not the one putting pen to paper here. She's dictating to her scribe, probably a male cleric, who may or may not have used a heavy editorial hand during the writing of the narrative.
Even so, there are still moments in the text when we glimpse a funky turn of phrase or use of image that screams "MARGERY KEMPE!" rather than "CLERICAL INTERFERENCE!" The most obvious moments of this happen when Kempe handles figurative language, as in the following passage:
"Daughter, you are obedient to my will, and cleave as fast to me as the skin of a stockfish sticks to man's hand when it is boiled, and you will not forsake me for any shame that any man can do you." (I.37.127)
This is Jesus praising Kempe's humility and obedience. Notice that he conveniently uses "homely" or familiar terminology with her—hey, a girl from a seaport town knows the properties of stockfish skin—and not obscure, theological, fancy-pants language.
Kempe treats us readers in a similar way. She has no intention of dancing around any issue, including things that are clearly TMI: "She lay beside her husband, and to have intercourse with him was so abominable to her that she could not bear it..." (I.4.50). Yeah, she doesn't mince words, even if she isn't writing them herself.