As suggested in the comments, some additional details about this post:
Please notice that this thread's purpose is to show other game companies' stance on abusive behavior, not the methods that they use to hand out their penalties. I am simply comparing the penalties that verbally abusive players can get in these games. I am all for improving the mute system but removing the mute penalty simply isn't a solution. There needs to be a penalty for abusive behavior.
Blizzard games (WoW, Diablo III, Starcraft II)
"We want to ensure that all players can fully enjoy their gameplay experience. Sometimes disciplinary action must be taken against disruptive players who are negatively impacting others' play experience or the service itself. Though taking disciplinary action is never pleasant, it is occasionally warranted in order to maintain the quality of service for all."
Penalty: Text warning -> Temporary account suspension (progressive) -> Final text warning -> Account closure
Why it wouldn't work in DotA 2: The game is free-to-play, all features can be enjoyed right from the get-go and therefore the game doesn't require spending time, work and money on it to access certain features. The game also lacks a ladder system and a ranked mode.
Call of Duty series (MW3, Black Ops II)
"Any user who is found to use aggressive, offensive, derogatory or racially charged language is subject to penalty. Any user who creates an emblem with sexually gratuitous images, racially offensive material or foul language is subject to penalty."
Penalty: Temporary account suspension -> Temporary suspension and removal of voice chat privileges -> Permanent ban from online play
Why it wouldn't work in DotA 2: Complete removal of voice chat privileges would be a big issue in this game. Voice chat is essentially more efficient than text chat at conveying information and a permanent voice ban doesn't allow for behavior improvement.
League of Legends
"Players shouldn’t need to rely on features like the mute button or language filter to engage with other players in positive ways. When a player verbally abuses another player and forces him to use the mute button, they have already created a negative experience for that player. More info: http://na.leagueoflegends.com/tribunal/en/faq/ "
Penalty: Email warning -> Temporary account suspension (progressive) -> Indefinite account suspension
Why it wouldn't work in DotA 2: Even though LoL's penalty system is quite efficient, getting one's account banned is far less problematic in DotA 2. Users do not have to grind to Account Level 30 to enjoy all the features of the game (runes, masteries, etc), do not have to buy characters and can fully share cosmetic items between accounts. Also, DotA 2 (again) doesn't have a ladder system.
"Here at En Masse, we are gamers first. We realize that people make mistakes, get heated, and sometimes lose their cool. We will look at the intent and context behind all violations of our Terms of Service and Rules of Conduct before taking action against your account. Our goal is to keep the game fun for everyone."
Penalty: Temporary mute ban (progressive) -> Temporary account suspension -> Account closure
Why it wouldn't work in DotA 2: Temporary and permanent account suspension would not do much. People can already create smurf accounts and, as mentioned before, there are very few disadvantages to losing a DotA 2 account.
Wargaming.net games (World of Tanks, World of Warplanes)
"Excessive profanity and inappropriate language is not welcome. It is suggested to ensure that the censor filter is switched on. The censor filter is not an excuse to break the existing game and chat rules, and excessive profanity will still be sanctioned. Typing in such a way to bypass the censor filter is prohibited. Insults, personal attacks, abuse or harassment are not tolerated on any level."
Penalty: Temporary account suspension (progressive) -> Account closure
Why it wouldn't work in DotA 2: See above. People losing their WoT accounts are probably crying though considering how time-consuming it is to unlock things in this game. (Interestingly, Wargaming.net have a specific rule that states that you can get a suspension for speaking non-english languages in the regular chat lobby... so apparently it's not such a farfetched idea.)
"One of the first things we dug into were the factors that contributed to a player quitting. [...] Losing a bunch of Dota 2 games doesn’t seem to cause people to quit. But one thing that did stand out in the data was the amount of negative communication between players. Put simply, you are more likely to quit if there is abusive chat going on in your games."
Penalty: Temporary mute ban (progressive)
As you can see, the penalty is much different than other online games which is understandably confusing... but unlike all the other companies, Valve does not hand out permanent bans for abusive behavior. All of these games have a competitive environment and yet Valve are the only ones trying to give players the chance to improve their attitude indefinitely.
To put it simply, if an aggressive, abusive player in DotA 2 has the same kind of behavior in any of these games listed above, in the long run they will end up getting a permanent ban.