I'll admit I do this quite often on work email which is, by the necessity of everyone else on the email chain expecting it to be so, almost always in HTML.

As it turns out, I have a bit of a list-based criteria on how I reply to emails on mailing lists, but, for better or for worse, have fallen into the habit of top-posting on most private emails. This latter, alas, is also becoming the norm as we enter the second (third?) decade of the "eternal fall."