Clee: it's really quite simple, IMVHO.
If the goal of planetkde is to syndicate blogs about KDE, then you should only aggregate feeds that are about KDE. The goddess knows mine isn't, except occasinally (you should use this one instead (it is boring and empty, though).
However, if the goal of planetkde is to syndicate the blogs of kde-related people, then you just aggregate them (with the agreement of the blogger) and that's that.
If someone posts something strange or sad or whatever, the others can post replies, encouragements, whatever, and life goes on.
Since it's your site, you are the one that chooses. I would prefer the second approach, though.