Coda has to interact well with all worlds, *BSD, Linux and even W*ndows.

  The interaction with each of those is not going to be smooth,
  partly because they are incompatible in one or another way
  and Coda has to comply with them all.

Sure, and in the linux case it means pushing coda.h changes back to
glibc, and having some way to avoid using old installed versions.
My point is that right now coda is off the rails of good CM practice.

  This means that "fixing" Coda for some kind of purity has a potential
  of making more harm than good. This is not _really_ crucial, I think,
  and there are also other challenges on the table :)

The point isn't purity - it's avoiding the kinds of problems that bad CM
practices lead to.   I agree, though, that this is far from the most
important issue.  I brought it up because it relates to an automake
retooling.