I may be just a pie-in-the-sky optimist but I think the duplicate communities thing will die down eventually. Natural selection will do it's thing and we'll all eventually settle in specific communities on specific instances.

Based on the nature of life itself all living things become specialized over time. This includes creatures, jobs, products, communities, etc. So what's likely to happen is some communities will die out or be abandoned while others will thrive and yet others will simply become more specialized.

Hypothetical example: /m/gifs on Kbin might become the place to find perfect loops and high quality/serious stuff while /m/gifs on some other instance might become the place for animated silliness.