Sorry I missed responding to those questions earlier, ljk. Better late than never.

We could subdivide Space/Science into multiple boards if we want to. But we'd have to deal with some complications. Traffic by topic is uneven, depending on events in the outside world. Lots of Mars traffic these days, but it's still episodic. Discussion of exoplanets is driven by discovery announcements. Etc. etc. So my concern would be that a subsidiary board could languish for long periods. Or that imbalances would arise, a trickle on one board and a flood on another, leading to continual restructuring of the boards in an attempt to balance the flow.

Another concern is social: Balkanization of the community by narrower interest. The tendency of people to cluster over time will create mini-communities whose interests might diverge.

Just thinking aloud, but it might be more useful to give people a way to filter or sort the Space/Science flow, so that they create virtual categories that match their personal interests. A search is an example of a retroactive filter, but topics could be filtered in realtime to display groupings of related content. "My Space/Science", to use the hoary cliche.

Everyone wants a search feature, including me. It's tougher than it seems, both for purely technical reasons having to do with the structure of data storage, and for conceptual reasons. The content of the boards is unique, and different search techniques are useful on different boards. For example, on CE it's meaningful to search for posts based on the known political leanings of the posters, but on SS that's a less meaningful (though in situations like discussions of space policy, not entirely meaningless) way to search.

Search is a high priority in the next generation of software. I'm motivated--everybody keeps bugging me about it!