[BobC]

I've looked at the reference provided for the Bronti spelling in the Fields, Osgood & Co edition and it doesn't say that Charlotte signed her name that way, it just refers to her as Miss Bronti (undotted i") but says her handwriting was "exceedingly small, nervous and poor, but quite legible". There are only two references in the book to Charlotte and they are both on that same page and are consistent in their presentation. No other lower case "i" present on the page is missing it's tittle.

Martineau's autobiography was edited by Maria Weston Chapman who I assume took a manuscript and transcribed it for publication, another point at which an error could creep in. However the prefatory note in the US edition does suggest that Harriet was happy with the presentation of the book so perhaps this is a red herring.

Even if we assume that the undotted i (with or without an umlout) is what Martineau wrote in her own autobiography it is not evidence of what Charlotte herself wrote.

Despite all this it seems likely that the book you are working on used some form of "i" so to revert to the original question it would seem right to follow Harry T and jelby's advice to leave it as is.

BobC

PS - just re-read post #8 where it says the reference to her signing her name thus is in Martineau's "Biographical Sketches" I also see in there that Martineau says that Brontë is an abbreviation of "Bronterre" !