In practice it is a good idea. In reality I doubt it can work. If chess.com detects someone using an engine then it is my understanding that their account is closed. If chess.com is not sure that someone used an engine, but think they might have, then it would be wrong to label such a person as cheating. The same argument goes for disconnecting. You may say it is obvious - but it is a matter of opinion.
Why not introduce a player fairness rating?

This would be super easy to abuse. You might know who someone is in real life, create a bunch of sock puppet accounts, and give that person a terrible reputation, all without fear of retaliation.

The real cheaters always use advanced proxys to hide their activity. Obviously they will blame somebody else for their own scandalous behaviour.
Implementation of more advanced cheating detection would be highly appreciated.

What in the name of Satan's unholy jockstrap is a Sock puppet ?
https://en.wikipedia.org/wiki/Sockpuppet_%28Internet%29

FIDE Chess Online Arena has implemented a "reliability rating".

Anonymous or not, I don't like the idea of an evaluation system. It will be abused to give negative marks to a person that otherwise did nothing wrong during their games, but the opponent they defeated is pissed off and rates them poorly for spite. I encounter sore losers EVERY day that I play online chess, so you can bet they would have a field day with a player evaluation system.
I think the OP is suggesting that the evaluation is made by chess.com rather than by other members (which I agree wouldn't work)

In practice it is a good idea. In reality I doubt it can work. If chess.com detects someone using an engine then it is my understanding that their account is closed. If chess.com is not sure that someone used an engine, but think they might have, then it would be wrong to label such a person as cheating. The same argument goes for disconnecting. You may say it is obvious - but it is a matter of opinion.
I agree it's a matter of opinion, on the other hand when you play a 1200 opponent, you fork their two pieces and you see them play a sophisticated combination to get out of the fork and win your rook..well..
I agree that ratings might not be the ideal solution, but that was just an idea. I play a lot of interesting games with nice opponents here, but it also happens very often to meet disconnecters, cheaters, people which start games and let you wait 10 minutes before leaving and the like. I'm sure this can be improved.

Anonymous or not, I don't like the idea of an evaluation system. It will be abused to give negative marks to a person that otherwise did nothing wrong during their games, but the opponent they defeated is pissed off and rates them poorly for spite. I encounter sore losers EVERY day that I play online chess, so you can bet they would have a field day with a player evaluation system.
I think the OP is suggesting that the evaluation is made by chess.com rather than by other members (which I agree wouldn't work)
I did mean the evaluation be done by opponents, but I'm aware it's complicated, so what you suggest (ratings managed by chess.com) is even better.
I am wondering why chess.com does not introduce a fairness rating for each player. Practices like disconnecting when in a losing position, or using the support of chess engines during games - which you cannot always prove, even though it's often obvious, should be subjected to the rating of your opponent. Rating could be anonymous, in order to prevent retailation.
These ratings might then be used as filters to exclude bad players when looking for an opponent, which would significantly improve the quality of games on chess.com.
Thank you