Personally, I think it makes sense to answer someone who sends you a plain text message in plain text. After all, he might very well have an email program that isn't capable (by design or by settings) to correctly handle an html-message if he can't send it.
So I think Outlook behaves smart, not erroneous.
If your IT dept has a support contract with Microsoft, they can ask. Please let us know their answer.
Im running office 2003 and have outlook set up to use word as my email editor.
The default is set to use HTML for all documents but when some emails come in as plain text, word wont change them to my default when i answer but keeps them as plain text....my IT department is stumped as am I........
im running windows XP on a laptop...