As far as I’m aware this was never the case as in only setting it to insert a note in HTML and not Text emails or vice versa. Avast 4.8 was the last version that differentiated in the in the clean notes (e.g. you could edit the content of it, using the Format of the notes) for HTML or Text emails.

It was either insert the clean note or not (see image from 4.8 ), not which to insert as that depended on the email you were sending. If this was only text based email it would be a text message, if an html only email then it would be the html message. If it were a multi-part email, e.g. it had two parts html and text, then notes for each would be inserted.