CG: Which data discs stack? And how do they stack?

Anything that doesn’t specify it doesn’t stack, stacks.

However some things that stack don’t practically stack—for instance, Offensive Buffs gives you Offense Up, Crit Damage Up, and a third one. But having Offense Up two or three or even fifty-eleven times doesn’t give more Offense Up than one instance of it.

tl:dr—if it says it doesn’t stack, it doesn’t stack. If it doesn’t say that, it does.