Quotations and Dialogue

Q. I’m working on a manuscript where the author starts many block quotes with lowercase words. Is this okay?

A. Yes. It’s a service to readers to use whichever case fits with the text that introduces the quotation. In legal or technical writing, linguistics, or literary criticism, though, the original casing might have significance, in which case you must retain it.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]