[PLUG] Unicode mystery

[John Jason Jordan]

As I read my mail this morning there are a couple posts to Plug-Talk by
Russell regarding FCC chairs. The text was interesting, but to me what
was even more curious was a mystery glyph in the subject line: "’."
From the context the glyph was intended to by an apostrophe. This glyph
did not render in Claws Mail. I copied and pasted it into a LO Writer
document, where it also failed to render, and ditto for Gedit. Looking
at the headers for the mail I find "User-Agent: Gnus/5.101 (Gnus
v5.10.10) Emacs/21.4 (gnu/linux)."

I can go to websites written in Thai, Devanagari, Chinese, Arabic, or
any other of the hundreds of writing systems in the world, and they all
render flawlessly in Firefox on any Linux computer that I have ever
tried. Similarly, when I occasionally receive an e-mail written in a
non-Roman script, it renders fine in Claws Mail. However, I must confess
that I am ignorant of the magic behind the display. These things have
always just worked without intervention by me.

I noticed that the glyph appears in Claws Mail and Gedit as a box with
numbers in it, specifically:

00
92

Assuming that this is the Unicode value, I used Fontforge to look up
what U+0092 is supposed to be, and it turns out to be "C1 Control
Character." Googling on what a C1 Control Character might be turned up
a Wikipedia page where U+0092 is defined as "Private Use 2: Reserved for
a function without standardized meaning for private use as required,
subject to the prior agreement of the sender and the recipient of the
data." WTH?

And having got this far I remember that occasionally text on an
otherwise English web site or e-mail has a glyph that does not render
properly. From past experience the apostrophe seems to be a common
culprit. So now I'm curious about what program(s) are producing
this unusual glyph instead of the intended apostrophe, and why. (I find
"Emacs" in the header above.)  It might be useful to know not to use
such program(s) when writing text for web pages. 

So I started my Wednesday morning with a bit of education. But I bet
there's more to the story. :)