Well, it is true that camps, which I was clearing right at that time, can get marked. Sometimes the mark happened just 1 second before I was killing the large monster.
As far as I noticed, the system is never marking camps which are already cleared. So that leaves just the suggestion of "the system shouldn't mark camps which are in combat".
I don't know if this change should be done, though. It is already pretty stressing for me to make sure to clear all these camps before Kindred to deny them the stacks besides having to have control over objectives like dragon and ganking. And they are already planning buffs for Kindred as far as I know and their winrate doesn't look that bad, so probably we should wait for these buffs to kick in instead.