Is there a font, available to -all- TeX users, that includes a glyph that can be recognized as the Unicode Replacement Character? I realize I can use XeTeX with a U+FFFD (or maybe any character not in the font), but I'm interested in using standard pdfTeX with standard LaTeX 2e and a pure ASCII input file.
The glyph typically looks like a filled black diamond with a white question mark inside it:
If no such font is available, what's the best robust strategy for getting such a glyph into a standard pdfTeX document (one whose input file has no Unicode or non-ASCII UTF-8 byte sequences in it) without using XeTeX or similar? Inserting TikZ commands? Raw PostScript?
Right now, for lack of a better solution, I'm using a \textbullet, simply because it's the boldest/blackest glyph I can think of, and it's available in most standard fonts.
Creating a custom font with one glyph in it is not really viable, or if it is it's a strategy of last resort, unless (perhaps) it can be done automatically and on the fly when processing the document each time.
(Reposted from the texhax mailing list: http://tug.org/pipermail/texhax/2015-January/021519.html; originally posed by Doug McKenna)