Dota needs MMR decay for inactive players.

The amount of people around 6000-7000 mmr who just glicko'd/recalibrated up 1500 MMR playing undying, then proceeded to never play again is just silly.

Whenever one of these players starts playing again, they're just ruining games for a thousand MMR. It's silly.

I've been gaming for a long time, the starcraft 2 system of "bonus pool" was, in my opinion, the best decay system.

For those who don't know, your mmr would decay X points for inactive period, those points would go into a "bonus pool". When you'd play, and win, you'd get double the MMR for winning, the points won would be removed from your bonus pool. So if you decayed 500 mmr due to inactivity, you could it back easily by winning 250 mmr worth of games, and getting 250 bonus pool as a reward.

In a way, I believe this would also help smurfing. People wouldn't just sit on MMR-trophy main accounts, and smurf to play. It would instead motivate people to maintain MMR on a main account.