If my account is on Blahaj and the community I moderate is on another instance like lemmy.world, and the user is from an instance we defederate from like hexbear, I won’t see the hexbear user’s comments (or even their user if I search for it) from my Blahaj instance, and so I don’t see a way I can moderate their comments on the lemmy.world instance I moderate.
Does this seem right? Is there any workaround?
(I guess I could make an account on the same instance as the community I moderate just for moderating that instance?)
It depends on where the community is hosted.
If the community is a blahaj based community, then when we defederate, we stop sending community updates to their instance, and we don’t accept any updates from people on that instance, so their posts to the community never make it to us.
Which is to say, it is technically possible for folks on the defederated community to post and reply to old stuff in the community that existed before defederation, but even then, it won’t reach anyone else. It will just stay on the defederated instance. And they will not get new content, so they aren’t secretly replying and interacting to current conversations.
If the community is not based on blahaj, and the instance we have defederated from isn’t defederated from the instance that hosts the community, then basically, you need to bring on other mods/alts from the instance that hosts the community.