I did some poking around and I've come to the conclusion that the description isn't picked up by the repo-add script. This is what's happening around line 156:

[foutrelis@foutboxd staging]$ bsdtar -xOf wormsofprey-0.4.3-1-i686.pkg.tar.gz .PKGINFO | grep ^pkgdesc | sed 's|\(\w*\)\s*=\s*\(.*\)|\1="\2"|'
pkgdesc="W"�rms of Prey is the new and free real-time Worms game.

The output is then evaluated leading to "-bash: of: command not found" and causing pkgdesc not to be set.

That aside, I noticed that the PKGBUILD of wormsofprey is encoded in ISO-8859-1 (that's what `file' reports anyways). Converting the PKGBUILD to UTF-8 (using `recode iso8859-1..utf8 PKGBUILD') and rebuilding the package, produces the desired behavior:

[foutrelis@foutboxd staging]$ bsdtar -xOf wormsofprey-0.4.3-1-i686.pkg.new.tar.gz .PKGINFO | grep ^pkgdesc | sed 's|\(\w*\)\s*=\s*\(.*\)|\1="\2"|'
pkgdesc="Wörms of Prey is the new and free real-time Worms game."

Moreover, when the package is added to a database, the description is saved and retrieved correctly:

[foutrelis@foutboxd staging]$ pacman -Si wormsofprey | grep ^Desc
Description : Wörms of Prey is the new and free real-time Worms game.

Closing, unless someone believes this behavior of pacman and its accompanying scripts is unwanted and should be corrected, I'd suggest we just encode our PKGBUILDs in UTF-8 when necessary.

Pebkac strikes once again. Thanks for the help :)