Would you call Moll honest? We mean, what else can you call a gal who tells us, in unflinching detail, about every crime she has committed and every morally questionable choice she has made in her long, eventful life? She spares few details, even the ones we wish she had kept to herself (like the whole incest fiasco), and in the preface, the character/author tells us straight-up in the Preface: "The author is here supposed to be writing her own history" (Preface, 2). Sounds honest, right?
But there's a catch. Our narrator is a notorious criminal and a skilled liar. Oh yeah, that. Moll successfully tricks or fools pretty much every single person she ever encounters. So, how can we readers be sure she's not fooling us too?
In fact, this possibly deceitful tone is laid out for us in the Preface, before Moll even begins telling her story:
It is true that the original of this story is put into new words, and the style of the famous lady we here speak of is a little altered; particularly she is made to tell her own tale in modester words that she told it at first, the copy which came first to hand having been written in language more like one still in Newgate than one grown penitent and humble, as she afterwards pretends to be. (Preface, 3)
Oh, so Moll told this story in Newgate language (which we take to mean crass), and not the humble language we're actually reading? Hmm. That throws a wrench in the penitent tone we think we're reading as Moll laments her many crimes. And later, the author-character tells us that he had to leave the more lewd and vulgar stuff out of the story completely. So Moll is even worse than she seems.
This means that while the story is being presented as a totally true autobiography, it's actually a censored one. As we read, we have to consider the possibility that Moll's honest and repentant tone is actually being forced on the book by the real author. Does that make Moll less likeable? Less trustworthy? And why do you think the author-character felt the need to change the tone in the first place?