I think the key for people who are confused about this is that it's necessary to consider the part after the "@" to be just as much a part of the community name as the part before it. There's no such thing as a community named "No Stupid Questions", with no @whatever after it, because all community names inherently include that portion.
As an alternative solution there are issues for "multireddit"-like features, this issue for Lemmy, and Kbin has one here.