Spoiler I'm not good with the editing in this type of forums ... However, playing today a random battle in hackmons, i get damage from spiky shield when my pokemon trait was Magic Guard. I was a little surprised and asked if this was normal. Since no good answer, I tried again to reproduce the stuff ( my pokemon wasn't shedinja, but is the same ) ( Ignore the comment in battle pls ) and the output was the same. I've tried to replicate on 3ds, but no one was Avaible to do so. Serebii, and other wiki doesn't list spiky shield as exeption ( Like Curse or struggle ) and on other simulator I didn't find the same problem. Shedinja ability is magic guard, so I dunno. Test it
I already created a fix for Spiky Shield + Magic Guard, because I am pretty sure that Magic Guard should prevent the damage (and it is already coded that Magic Guard prevents Rocky Helmet damage). The fix can be implemented once the in-game test is done
Confirming, no recoil Edit: I did a double battle with Frustration on Clefable and Rocky helmet Chesnaught, I first used spikey+Frust, no recoil, then attacked and no recoil as well