User blog comment:B214/Volume 23 discussion blog/@comment-175.136.214.240-20171016073623/@comment-103.27.61.101-20171027031244

Issei can use dragon blast to achieve the same result and then everyone will go "He is that strong yet he has a stronger mode" which will show off even better. By hiding dxd mode he has an ace which can be used for surprise attack. The dimension is sturdier is it won't be destroyed to create black hole to ensure safety for everyone, the mountain and scenery aren't made to be sturdier, they don't do that. Like I said dragon blast can destroy a city but Issei uses dxd mode so he is weak.