Nice! Hadn't thought about that. In my head I was editing the meta tag of just this category, but obviously now it's the meta tag of all categories. Thanks for the tip, 'cause I indeed want to give every category a different description.
It seems Datafeedr starts to work for me just fine! I found a temporary solution for my other problem (see my other post), but I'm still wondering about the 'read more' code. But all the other things seem to work nicely now, after some quick adjustments (both language and style).