It might just be a correction, nothing more. I've done the same in the past in the interest of improving the original comment. Perhaps it could have been made clearer (e.g., "note:", s/1930s/1920/). I'm not sure you can read too much into it.
When pedantry serves as a roadblock to honest, charitable discussion, I agree :) I've written plenty of comments only to not-submit them, and deleted others right after posting. I've really tried to give people the benefit of the doubt, ignore small jibes if I can, and try to understand where people I may not agree with are coming from. After all, if I can't understand them, I'm not sure I can ask them to understand me. It's a work in progress. :)
PS: And actually, given their other follow-up comment,
