Opponent A plays the PLOT card " Mad Kings Legacy"

Opponent B has Beric Dondarian in play already with the attachment Flaming Sword attached which states " Attached character gets a +1 STR and cannot have its STR lowered by card effect.

Does this mean that i cannot remove this attachment as the result of doing so will mean Beric's STR is lowered ?

Thanks

Lowering str is not the same as removing an attachment that gives an opponent +1 str.

Lowering STR effects (burn) targets the character while attachment removal targets the attachment. They are different effects.

No. Cards and effects that lower strength specifically lower STR with -1 STR, -2 STR, etc. If you remove a STR bonus(+1 STR, +2 STR, etc.), that is not the same as lowering STR. It's considered removing the STR bonus.

If removing STR bonuses were considered lowering STR, then there would be a lot of issues with keeping track of bonuses that expire at the end of the phase and challenge. It would be impossible to keep track of all of that.