I understand that, but the “dubious” comment would still appear in the comment thread on both instances then, and that can turn into a problem. How do you deal with it?

Just to make an example: I moderate a community about Breath of the Wild, where content about the sequel Tears of the Kingdom are discouraged so that people who don’t own that game yet won’t have to worry about spoilers. There are also communities about both games, or even just the sequel, where “spoilers” simply aren’t an issue. Now imagine someone makes a post that appears in both communities, and the comment section contains content related to the sequel. How would you deal with it?

• Remove the comments about the sequel because the BotW community doesn’t allow spoilers? That’s a surefire way to piss off anyone subscribed to the TotK community, because they were simply discussing content they’re subscribed to and won’t understand what they did wrong or why their comments keep disappearing.

• Let the comments stay because the TotK community allows them? That’s a surefire way to piss off people subscribed to the BotW sub, as they were promised a spoiler-free browsing experience and now read about stuff they didnt want to read about. You cannot un-see spoilers, so “just deal with it” isn’t an option.

• Make it so that those comments are only displayed in the TotK community but not in the BotW community? That’s what we have right now - separate comment sections for each community. If you merge the comment sections and then retroactively have to sort out which comments are or are not displayed in the other sub, it will be an unneccessary extra workload for the mods as you can barely automate such a thing. And you would have to check every comment again as soon as someone makes a crosspost to a third, fourth, fifth community, as this would add extra rules that would make comments that were formerly comepletely fine suddenly not okay anymore.

Now this is an example where the issue are “just” gameplay spoilers, so it’s not exactly the end of the world. But once this happens to communities with different rulesets about politics, religion, NSFW content, things that are illegal in one country but not the other, and similar highly explosive topics, it will turn into a moderation nightmare to keep the comment section fair for everyone.