Guido van Rossum writes:
I don't know about the line breaks, but in recent weeks I've found myself more than once having to remind myself that inside interpolations, you must use the other type of quote.
My earlier remarks were specifically directed to line breaks. I see the point, but I think the question should be readability, as David points out. I don't think there's a problem with the opening quote in your example. Even in an ordinary string literal it's obvious to me that the embedded quotation marks are not intended to terminate the string: s = "Here is a singleton " and here is an initial for "something." But how about that last quotation mark? I tried to construct a similarly visually ambiguous f-string where braces "hide" the embedded quotation marks, and couldn't do it without a trailing quote followed immediately by an embedded literal line break. So I'm cautiously sympathetic to this extension, as long as embedded line breaks are not permitted in singly-quoted f-strings. However, I myself will almost certainly automatically "correct" such quotation marks if they are allowed. So this is unlikely to be a plus or a minus for me. Steve