I am using debconf-set-selections(1) to preseed configuration settings
on a Debian sid system. One of these addresses Fontconfig's subpixel-
rendering feature; I want to completely disable it:

    fontconfig-config fontconfig/subpixel_rendering select Never

When fontconfig is installed, however, the default value of
"Automatic" is made effective, ignoring the preseeded value. I have to
manually reconfigure the package and select "Never" in order to get
the desired setting.

The package should be checking for extant debconf settings upon
installation, and honoring them if they are found.

I reported this bug a while ago in Ubuntu:

https://bugs.launchpad.net/debian/+source/fontconfig/+bug/262089

However, it ceased to be an issue for them because they got rid of the
debconf questions altogether. (Is there any desire to harmonize the
fontconfig packages between Debian and Ubuntu?)