If someone does not point out when you are making a mistake "without
realizing it", how will you ever know you are making a mistake?
It would seem thunderbird enables both "send as HTML" and "start my
reply above quote" as default. Both have now been modified accordingly.
I'm still not fully acquainted with the nuances of the program yet. I
apologize for any annoyances.
One other setting that may help you, but is kind of hidden away, is
the option to set the type of email sent to specific domains.
Edit --> Preferences --> Composition --> General --> Send Options
Mikkel