This is the exact response from riot, copied from a ticket I sent in about three months ago:
Hey Chimpanturticorn,
The LeaverBuster system targets players who have a tendency of leaving or AFKing in games, whether it was intentional or not. For this reason we will not remove a leaverbuster punishment on an account. Keep in mind, a leaver or AFKer can have dramatic impact on the game; even leaving for a short duration and coming back to complete the game results in a period where a team has to play 4v5.
We understand that emergencies can occur outside of our control which may take us out of the game, that’s why Leaverbuster is designed to only take action after a series of incidents have been observed.
Continuing to leave games will result in scaling low-priority queue restrictions that will increase the time you must wait before entering a lobby. The only way to remove your Leaverbuster status is by playing games from start to finish without interruptions. If you are having connection issues or encountering bugs, don’t queue up for a match, take some time to troubleshoot the issue. If needed, I can send you to our tech team for assistance.
Econetics
Player Support
Shuriman Acolyte
Shurima?