I believe this has been taken care of since.

This isn't bogus, the same thing has bugged me and it's a real problem 
when reading, for example, mailing list digests from yahoo groups, 
google groups, mailman, etc. That said, I've tried to find a way to 
tweak the algorithm myself in the past and haven't been able to.

We dim everything after the signature block separator ('-- ') - so 
there's nothing we can do about this.  If those quoted blocks appear 
after the signature separator, by definition they are part of the 
signature.  If you can come up with an algorithim to determine what 
parts after a signature block separator should not be dimmed, that 
would be great.

When 'dim signatures' is ticked (or set to true), it dims everything 
after the signature - included any quoted text.  It does however 
display the 'hide quoted text' options - so clearly recognises there 
is quoted text (a forwarded message), but it does not display that 
quoted text in other colors - so it is next to invisible.