Some Fancy Pants Editor Tools Have No Effect

When I tweak the formatting with BBCode it’s applied but the Editor’s formatting tools are broken. Specifically, the tools in question are Bold, Italic, Quote, and Inline Code.

The Discourse software on which this site runs uses Markdown as its native formatting system and offers BBCode support as a convenience. When I use the Bold, Italic, Quote, and Inline Code editor buttons I get the Markdown tagging I would expect to see.

Here’s what I see (I couldn’t even post a link via the hyperlink tool):

I use Firefox Legacy.