I finally figured out why. It's described here as
Inkscape written in C++ (libstdc++.so.6) uses libgtkspell (written in C) uses enchant (written in C) uses aspell written in C++ (libstdc++.so.5) -> crash
I now officially wish painful boils onto the misdesigners of ELF (it was their fuckup that causes that crash, see rant here), on the people who designed C++ and it's misshapen inbred ABI, the implementors of the GNU C++ standard library, and whoever wrote the aspell RPM without noting the dependency on compat-libstdc++-33, and whoever decided that a vector draw program really really needed to spellcheck words.
(And no pointing and laughing from the Gentoo folks, this can burn you guys too...)