bug#12054: 24.1; regression? font-lock no-break-space with nil nobreak-char-display

[Drew Adams]

> >> Why should a character-alternative expression care whether the
> >> representation is unibyte or multibyte?  Isn't that a bug?
> 
> There are many different ways to interpret this, and I can 
> give you one where the behavior is explained without paying
> attention to multibyte/unibyte differences.
> 
> \240 in your string means "the byte with octal number 0240".

OK, so then do you think this should DTRT? 

(font-lock-add-keywords nil '(("\\(\302\240\\)+" (0 'foo t))) 'APPEND)

I'm guessing it shouldn't, because IIUC the buffer in fact contains only the
single raw byte \240 and not the multibyte sequence of two raw bytes \302 and
\240.

But I barely understand this stuff at all; I mostly misunderstand it still.