I completely agree with Keith. Text/html was a mistake.
That's like saying richtext was a mistake.
If you are referring to text/richtext, then there is in fact a broad
consensus that it *was* a mistake. That's why text/enriched was devised,
after all.
The fact is that the MUA's are blindingly violating the
HTML specification and making it an application-specific
format. You can hardly blame text/html for that.
It isn't a question of blame, it is a question of whether or not agents have
been generally able to construct HTML objects that are legible without any
formatting. In hindsight, the answer to this question has proved to be
"no". And since text/html's utility was predicated on the answer being
"yes", it was a mistake to have defined it.
Ned