Query: Should there be additional ligatures --<hyphenchar> and---<hyphenchar>?

[KNAPPEN@VKPMZD.kph.Uni-Mainz.DE]

The following problem was reported to me:

If you are using T1 encoded fonts (it doesn't matter which flavour) and set
the \defaulthyphenchar to 127, as recommended,

and you are using Bernd Raichle's extensions to the hyphenation pattern 
(t1hyph.tex),

Then the following situation can occur:

If your are setting an emdash without spaces between the words, and it falls 
at a line break, then there is a <hyphenchar> inserted after the emdash, 
which is obviously an error.

It is not clear to me, how to resolve this unfortunate situation:

(a) Change the hyphenation pattern to disallow a line break in this 
situation and similar ones. If there should be a line break, it needs to
be explicitly requested by the user.

(b) Add ligatures <emdash><hyphenchar> -> <emdash> and an analogous one for
the <endash>. Unfortunately, this means changing the metrics of all T1 
encoded fonts.

(c) Other solutions? (Use endashes with spaces instead of the victorian looking 
emdashes ;)

(d) Are there unwanted side effects of proposals (a) or (b)?

Yours, J"org Knappen.