Thanks to @Gower, we already have a thread aimed at clarifying the norms that affect how moderation rules play out on the forums:
That thread even has precedent for being shut down for lengthy cooldown periods, which might end up happening in any conversation about the new norms, too. 
But since for now we’re talking about it here: Getting suspended or banned for “soaking up too much moderator time” or similar is a necessary fallback rule on pretty much any forum. No ruleset can capture all the ways someone might be seriously disruptive. It’s rarely that hard for an asshole to find some perch from which despite breaking no rules they’re still ruining the quality of the community.
In the case under discussion – where someone’s been running a toxic forum adjacent to ours that’s kept creating spillover problems despite repeated (but one-sided) efforts at a solution – I have complete sympathy with invoking the principle.
At the same time, it’s a principle I’d advise any mod to use extremely sparingly, as a last resort, not letting it slip into becoming business as usual. (So, as in this case, try to come up with a rule whose application means you won’t have to fall back on the “mod headache” rule in similar future situations.) Otherwise it can readily turn into an ostracism machine, where a person whose views are unpopular among a big enough minority of forum members finds they either have to shut-up-and-sit-down or get banned for generating so much friction.
When those people’s views aren’t rulebreaking, just unpopular, that kind of outcome is in massive tension with the vision Bryce articulated of an inclusive, respectful, and compassionate community. We end up excluding good people and intimidating and disappointing others.
The more mods slip into relying on “they were just too damn much trouble” as a principle for shutting people down – or other justifications whose tone verges even closer to “this ain’t a democracy, kid, and we’ll run it however we like” – the more we’ll end up with fear and resentment as prominent community characteristics, and the fiercer the periodic bursts of backlash will be.
So to anyone who’s reacted to that justification with instinctive queasiness: I sympathize with the instinct! I don’t think you’re arguing in bad faith. I just think we really disagree about the potential impact of crapfest racist troll-farms.
Thanks to anonymity and the asymmetrical impact of assholishness, the culture of online spaces naturally trends toward “sewer” over time. An unmoderated forum that celebrates slurs and viciousness can degrade the culture of a neighboring forum pretty fast if you let them, especially if they exhaust your volunteer mods.
When you realize that a prominent author is leading part of your community that way, and the first couple things you’ve tried to deal with the problem haven’t worked, decisive action can be better than keeping experimenting with more tweaks to the rulebook.
To the handful of folk who’ve offered some version of “the Discord is irrelevant, why even share screenshots from there, only evidence of problems on this forum should be relevant to rule enforcement and/or mod exhaustion” – if all I’d seen were screenshots of trolls and harassers appearing repeatedly on/around the Aura Clash thread, I’d be a lot more dubious about banning the author. What reason would we have to think that’s his fault? That, to me, would be the “too much work for the mods” ban in its worst form…a troll brigade hits a thread, and the author gets punished for it.
But seeing that cultivanon’s been cheerfully serving as ringmaster of a next-door troll circus is what brings me onboard with the decision to take more drastic steps.
(Edit: removed an aside about cultivanon being willing to moderate for some things, since @fsix has called the accuracy of that take into question and it’s not central to my point.)