User blog comment:Kaze Tsuki/Critical Boost/@comment-24570336-20160820162203

To answer your question, I'll let you look at these situations:

A) 90% Crit * Normal Enemies (100%) > 70% Crit (Because 70% is the cap)

B) 90% Crit * Crit Resistant Enemies (50%) = 45% Crit

C) 90% Crit * Crit Immune Enemy (0%) = 0% Crit

Therefore, Yes, Crit can stack, as long as the final Crit rate is 70% or less.