Thank you for the bug report, and for going to the work of tracking down what was happening.
Erlang debug info was deliberately stripped out in order to make the erlang runtime smaller so it could fit on the CD, as we shipped CouchDB on the CD in Ubuntu 9.10. I have not figured out whether it is possible to ship erlang debug info in a separate parallel package like we do for C programs. So the other solution I had come up with but not gotten around to setting up until tonight was to make a PPA with a rebuilt erlang package that included the debug info. This way we still have a small erlang that fits on the CD by default, but Erlang developers that want to use dialyzer and the debugger can easily get alternate erlang packages that include debug info.
I believe this bug should be closed as wontfix. I am aware that Sergei has changed the debian packages to build with debug info included by default, this is a reasonable choice for debian but not for Ubuntu. Sergei has kindly left the patch in place and just commented out because Ubuntu still needs the smaller erlang runtime, so we can still easily merge from debian to ubuntu.
I've now created a PPA including a rebuilt erlang with debug info here: https://edge.launchpad.net/~erlang-dev/+archive/ppa
The patch from stock ubuntu 9.10 is a trivial one-liner, commenting out a line in the quilt series file.
To add this ppa to you Ubuntu 9.10 machine, type:
sudo add-apt-respository ppa:erlang-dev/ppa
If it would be useful to people developing erlang programs, we could set up a parallel PPA that had even newer versions of Erlang in it with debug info turned on there also, so that it's easy to get the very latest erlang release to develop against.