Open is PvP, not PvE. When there is another human involved, and rules you are expected to follow.
Speak for yourself. This is why there are rules, and if caught you will be punished. It's not for you to decide who's day it ruins.
Your crappy internet is not my problem.
Until someone annoyed enough to screen record all of their play catches you doing this, opens a support ticket with video evidence, and you get the ban you deserve.
In a MOBA? Your team is down a person, which statistically torpedoes your winrate. The other team gets an easy win they didn't have to work for, which feels remarkably hollow.
You'll notice I was speaking specifically of league of legends. Players have been banned for repeated disconnects. Given that the developers here acknowledge it as an exploit, similar measures should be expected.
All accept for the fact that when someone combat logs doesnt effect anyone or the game. Other than the person who wanted the cheap thrill of blowing up someone with no reliable means to defend themselves.