How do we avoid fragmentation? Where there's overlap, are there reasoned opinions on how to converge (eg matching instance policies to the audience)?
Do we just encourage communities to peer-link until critical mass develops and community activity-levels speak for themselves? Or is that just likely to split the community until community owners promote migration towards a 'common space' for each type of content?
I'm concerned that the lack of an effort to make similar communities visible will result in accidental cliques forming, not because the communities are meaningfully different, but because a large portion of their membership are oblivious to the existence of their peers.
Having separate groups, serving the same purpose surely doesn't benefit the participants. It may even turn users away, incorrectly communicating a lack of activity or misrepresenting the true number of like-minded participants.
The only way I can see to avoid this now, is to actively engage in peer-linking. The coalescing of redundant splits in communities can happen later (hopefully with some future assistance from the platform).