One way to MakePeopleGoAway.
I feel that an individual rarely has a duty to ostracize someone else for the sake of a group. However, they have a strong duty not to exclude someone else unduly. Since everyone will have different views of the magnitude of the problem with a given individual, it is hard to get everyone in a group to DissuadeReputation at the same time. The "most accepting common denominator" will win out and it will rarely be possible for the group to totally cut off interaction with an individual, although it will be possible to attenuate interaction.
This dynamic gets even more problematic when DissuadeReputation is chosen as the result of an incompatible personality rather than because the target did something wrong. Even if the target's personality is incompatible with the group, they might be compatible with some of the individuals within the group. There is no reason for these individuals not to work with the target outside of that particular group. Hence, the target will have secondary ties to the group even if they do not directly contribute.
Although I am mostly hypothesizing that this is the case in an online community, I have seen this happen in RealLife.
I should note that the "duties" I talk about here are somewhat weaker than your basic moral duties such as the duty to keep your promises, etc. They're more a matter of "niceness" and "good practice" than hardcore "moral duties". For example, not excluding someone from a group unduly is not a "moral duty" but rather a nice thing to do, and also good practice (to prevent cliqiness). Excluding someone for the sake of a group (DissuadeReputation) is also not a "moral duty" but rather good practice in some circumstances (to get harmful individuals to go away).
I think that DissuadeReputation, as originally stated, is a good idea and should be revived, but we should take care not to (unknowingly) cross the line into PunishReputation. If someone is not encouraged here or listened to, that's DissuadeReputation. Once people start criticizing that person, or telling them to leave, or discussing them as if they are a problem, the line has been crossed.