How does one determine if and when such as user should be asked/made
When your interactions as a moderator and member of the community with the user occur primarily due to complaints of others, it is time to ask them to take a break from the community.
And how should one go about it?
I think this will depend on the maturity level of the user. Presumably, asking them to take a break isn't the first course of action you are taking. In general though, a three strikes policy for these well meaning, engaged users is a good method. Starting with a simple side conversation discussing how the user comes off to others may be enough to get the user to contribute in a more meaningful manner.
If that doesn't work, another conversation explaining community feedback regarding the user, moderator feedback regarding the user and explaining that a break may be necessary is important. At this point, make it clear that you aren't performing any actions, but that your time as a moderator is being increasingly devoted to interacting with just this person and that is not a positive sign.
Finally, on the third interaction, it falls to your communities policies. Issue a temporary suspension but be sure to talk with the user. Don't make it a public shaming for a couple reasons.
- If the user has 'supporters' all this does is open up an official spot to complain. It also starts the conversation with you laying down the law. They will find out eventually, and you should address it when it is brought up, but it is not something that needs to be laid out for the entire world to see.
- It embarrasses the user. Assuming they were a contributing member and well respected, all you are doing is pointing at them and saying "this is a bad person".
The conversation with the user should explain the reason for the suspension. It should also explain they'll be welcome to return after the suspension if they can contribute in a more constructive manner. I would also mention your community's policies against repeat offenders. I don't believe the three strikes should start over when they return. It should continue. Strike 4 should have a longer period of suspension, not another side conversation asking them to behave.
One thing that is important for a user to recognize when they return from a suspension, is that the community has moved ahead while they were gone. Rehashing old arguments that may have long been solved in their absence is not constructive.