If you increment something for second time, Karma should ignore it. Also, if you change your vote from positive to negative or in the other way, it should remove your old vote.
20:11:27 nyuszika7h | ^karma ChanServ
20:11:32 nyuSupy | ChanServ has neutral karma.
20:11:37 nyuszika7h | ChanServ++
20:11:39 nyuszika7h | ^karma ChanServ
20:11:43 nyuSupy | Karma for "ChanServ" has been increased 1 time and decreased 0 times for a total karma of 1.
20:11:46 nyuszika7h | ChanServ++
20:11:56 nyuszika7h | ^karma ChanServ
20:11:59 nyuSupy | Karma for "ChanServ" has been increased 2 times and decreased 0 times for a total karma of 2.
If you increment something for second time, Karma should ignore it. Also, if you change your vote from positive to negative or in the other way, it should remove your old vote.