Theres been issues with the communities table since the update and it hasnt been fixed yet since there hasnt been time to do so. Same issue that hit the person table but that one was fixed after the db maintenance we had
I havent been the one looking at the database but im assuming itll be a similar way to how the person table was fixed. Theres essentially duplicate entries for certain communities atm
are there no references to the duplicates from posts? if there are and the duplicate rows are just deleted it'll cascade deletion and purge all those posts from the db as well