I think there's no explanation on how MC buff effect can be shared to other player(s)? This might be important for those who play as a team.
This is a rule on effect stacking that I know of: Summon call effect seem to stack with party skill effect. ex: Lyria buff skill with say Freyr or Lucifer summon, the attack buff can stack same with MC skill effect such as Mechanic's Refuel or Rage skill.
since Freyr call effect provide a massive attack boost, this mean that if the skill can't stack it should give a "no effect" message when applied, call Freyr first then use party skill to confirm this, I have also check the damage they done and they do stack.
I still don't know how effect stack with weapon CA effect. If the Summon call effect and party skill effect do not stack maybe there's a bug on the game side and be treated as such? Also a skill or call effect that consist of buffs and debuffs might play outside of this rule, an attack that give buff and skill such as heal that give debuff(s) fall under this category.
My theory is, maybe there's an invisible mechanics in the game for buff, debuff, and mixed(buff and debuff)/special slot? When say a buff slot is filled with attack up then other attack up can only overwrite or give no effect. However another attack up can still take slot in the mixed slot.
Summon call effect and CA effect fall under mixed slot regardless on how sometime summon call effect does not give damage. A party member skill can fall under the category of either buff, debuff, or mixed.
Buff/debuff that give more than 50% boost go in mixed/special slot, even if there's a buff or debuff mixed with them that only give say 20% defense down if there is a buff or debuff that give 70% up then all those series of buff and debuff will all fall to the mixed/special slot.