No. There are no justifiable use-cases for the majority. to have several accounts
Sure, several, but feel free to debunk the for me most important ones:
1# privacy, allows users to voice unpopular opinion without fear for the main account.
2# security, users have a separate account for less secure systems.
Id even add #3 money to this list, AFAIK no campaign forbids users to have different accounts joined on a different campaign.
The occasional constructive user or two may have more accounts, but those are a very tiny minority. The rest are shit posters / account farmers.
What do you base this on?
I base that on the time spent moderating + managing hundreds of users in Bitmixer. I'm most certain that managers and moderators (those that are tackling spam in one way or another) are the most qualified people to talk about this situation, unless there are other individuals that are somehow involved (similar amount of time/effort).
In this case I would say Im qualified due to my work for BadBear. Lets assume it is as you say an the majority of multi accounters are shit posters. Why punish everyone without a way out or a chance of redemption? Why are you unable to let this get handled by mods? Why do you claim a duty that is not yet yours, as your rank among staff is not yet high enough?