How was I able to attain more than 100% kill participation with D. Va?

I believe this is due to someone leaving and another person joining and ending the game with fewer deaths than the other person had when they left. From what I can tell, it seems to calculate the kill participation percentage by # of eliminations you get / total # of deaths other team has. So if you have 100% kill participation, and the person on the other team who has the most deaths leaves, and someone else joins and ends the games with less deaths and you keep your kill participation close to 100% after that, your kill participation would be over 100%. This would also occur if someone left and no one replaced them. I have noticed a jump in kill participation when this happens, and a number of other people report this happening to them.

Any kills done after a round ends in Control Point maps such as Lijiang Tower count for personal stats, but not for the match's stats. So an elimination you made after a round's end will increase your own eliminations, but not the team's total eliminations.

With that it's possible to pad "card stats", making it possible to achieve kill participation higher than 100%.