I have 3 abilities linked to a +5% attack power mutagen granting a total of 20% attack power increase. The silver sword damage displayed is 527. If I now exchange two abilities that are NOT attached to the attack power mutagen the damage falls to 514, exchanging again leads to 501 and then finally to 487 damage. Further switching around of those two abilities don't change the damage.

So does this change the damage or is it just a display bug???

Maybe you lost adrenaline while you looked at the stats and thus your damage decreased... is that possible?

No, because I can get the damage display go up again by moving abilities around.