Viewing only one message as original HTML in Thunderbird

This Lifehacker article has some explanation on what's going on. What it basically says is that when the sender types in a ":)" character, their Outlook automatically converts it into a smiley rendered in the Wingdings font. As far as I know, this happens when Outlook uses Word to edit email messages.

At the moment, I'm on a box with Outlook installed, not Thunderbird. Is it possible for you to change the encoding to ISO-8859-1 to see what happens?

I found a workaround that worked well enough for my purposes.

The instructions from http://support.microsoft.com/kb/831607 (in Outlook 2010, but there are instructions for earlier versions of Outlook there too) to convert the HTML message to plain text before replying to it. The option is rather deeply buried in the settings, so it's a bit of work to get to, but perhaps not quite so much work as cutting and pasting text into and out of a text editor to achieve the same result.

And I'm thinking I might like having all my incoming mail appear in plain text, so I'm going to try leaving the new setting on permanently! If I want to see a particular HTML message formatted, it's just a matter of a two clicks of the mouse in the "InfoBar" above the message header.