Can replay transactions effect both chains? or just the minority hard fork chain? Can a seg2x transaction be replayed on the main bitcoin CORE chain?  

I was reading that only the minority hard fork would need replay protection and that coins on the main majority chain would be safe
Can a seg2x transaction be replayed on the main bitcoin CORE chain?


yes


  only the minority hard fork would need replay protection and that coins on the main majority chain would be safe


(a)this is wrong (b)nobody knows what chain will be major, what minor