Before we get started, let's establish facts:
1. It's impossible to be 100% sure if someone combat logged, or if their connection was lost/disrupted. Not just in P2P, but even with dedicated servers.
2. We want to minimize the accidental punishment.
3. In ANY game with a dedicated server, disconnecting means you'd die anyways. REGARDLESS of the reason.
4. In many popular multiplayer games, There are HARSH penalties for leaving.
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How does this work in other games?
1. **Halo** - [Read this from the Halo Subreddit for perspective](
https://www.reddit.com/r/halo/comments/55dbfb/can_i_complain_about_the_ban_hammer_a_little/) Due to the crazy number of people who were quitting Halo 5 games early, 343i implemented *harsh* bans. ANYONE who quits cannot log back in for 30 *minutes* which doubles with every subsequent quit in 24 hours. Numbers are way down. Halo 5 is the most relevant as previous halo games did not have harsh quit penalties, and this led to extremely high quit rates.
2. **Overwatch**
https://www.vg247.com/2016/06/23/ov...petitive-play-matches-are-not-messing-around/ Tl;Dr: you get increasing bans over time for leaving.
3. **DOTA2** Leaving Penalty is damn harsh. Here's a complaint post
http://steamcommunity.com/app/570/discussions/0/882966056336164399/?l=polish
4. **Counter Strike** The ban systems works as follows:1st infraction: 30min. 2nd infraction: 2 hours. 3rd infraction: 24 hours 4th infraction: 7 days. Any one of these infractions get rest by my understanding after a week.
5. **RuneScape** If you log out mid-combat, your character persists in the game, and will die.
Note: I chose a mix of MMO's, FPS games, MOBAs, and F2P as well as Paid games. Why? because Elite costing money is no excuse for not punishing combat loggers.