Automoderator rules took care of 90% of the spammy issues. Some things were obvious and chronic, and like porn vs. art, "I know it when I see it." Incivility was pretty easy to identify and call out, but there were a few people that toed the line and would seep toxicity into the sub rather than dump toxicity flamewar-style. They'd never do any one thing to get themselves banned, as they'd very carefully adhere to the letter of the law (sub rules). For a while there was a lot of SPAC hyping, to the point that I had to create a rule just for that. More on that later.
Topic-wise, most of what people viewed as toxic was the drama around Tesla vs. the rest of the industry. There would be people wrapping around the pole on EPA range, charging infrastructure, fit-and-finish, software features, sound isolation, handling characteristics, straight-line 0-60, buying experience, their opinion of Elon Musk, FSD, the existence of a steering wheel, etc. etc. People would often appeal to the mods to try to either take sides or tone down the heat.
Occasionally people would pop in with an opinion on hydrogen fuel cell vehicles, which to me seemed like a reasonable topic to discuss in a forum about alternative-energy propulsion systems for vehicles, and they'd get shouted out of the forum as not "EV" enough. (Or worse, "Hydrogen is a pipe dream that will never happen to shut up about it already!") Gatekeepers would insist that the only thing anyone could talk about was passenger vehicles with large battery packs, or maybe a picture of an electric bus every once in a while. Posts about electric bikes or boats would get ignored or called out as, "Not the right kind of vehicle for this sub."
Inevitably the mod queue would get filled up with reports for such topics the gatekeepers didn't think are "on-topic" enough. This was the grey area where I had to make a call as a moderator. If a SPAC hype post got downvoted about as much as an electric bicycle post, by what criteria could I justify removing the SPAC post and letting votes decide what happens with the e-bike post?
My solution was to pop it up to a meta-conversation in the forum. "Let's talk about the rules. I've noticed posts with this characteristic or that. What would we think of disallowing posts like this and allowing posts like that?" There would be opinions on both sides, but ultimately I had to rely on my own judgment of "What's reasonable?" when making the final call on the rules.
Moderation of a public forum is very much a human problem, and there will always be corner cases. It reminded me a lot of what I learned in a graduate class I took on intellectual property law back when I was in school. There will always be a contour, and there will always be "test" cases that push and pull on the boundaries. Having rules ("laws") that set the groundwork for decisions is important. The process for establishing (and changing) those rules should be transparent and inclusive. No rule is going to have 100% support from all sides, but to build a system that works, we need to be able to agree on the process, respect the rules that we converge upon, and challenge rules in a civil manner that become obsolete as the world moves forward.