>> {\rant ...breaks...other framing errors...}
> The problem with this is the fact that most UART chips can't
> distinguish between the two.  Traditionally, a break is 300ms
> long...much longer than a byte at even low baud rates.

300ms to the byte is 30ms to the bit is about 33 baud.  I've used baud
rates lower than that, but only for very special purposes (like
directly driving a light with the signal, for a human to look at).

> A UART can only really treat this as a framing error. :-(

But it's a very special type of framing error; the signal does not
return to the mark state at any point during it.  Framing errors from
noise generally don't extend for hundreds of milliseconds and
(approximately) never last for hundreds of milliseconds without any
return to mark voltage.

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