You don't actually need special software to create closed captions: a
text editor will do fine. It's just a lot easier and less error-prone
with special software.

I think it's a great idea, and a boon for those of us who actually
post in two different languages. I haven't tried it yet, but am
certainly going to experiment when I have the time.

It might be a good idea to make a bit more obvious that captions/
subtitles are available, and how to turn them on. Right now, you have
to know that the little pointy-up arrow indicates that captions are
available, and four separate clicks are required to turn captions on
and select a language -- more if you're not fast enough and the menu
closes up again.

And now for my famed nit-pickiness. The German translator translated
"captions" as "Zwischentitel", which is the definition you may find in
a dictionary. However, technically, "Zwischentitel" actually means
"intertitle", which is an entirely different thing altogether. I think
the confusion set in because in everyday speech, "caption" can be used
to refer to any kind of subtitle or intertitle, or the translator was
struggling to differentiate between "captions" and "subtitles" in
German. However, there is no difference in German: "Untertitel" is the
word used regardless of what language they're in. In fact, this
translation error makes a whole nonsense of the German "Captions /
Subtitles definition" page.