Yeah this is on purpose. A trap or counter effect (such as soul trap or spiked shields) only triggers if the damage is a direct result of your opponent’s attack.

There’s two other ways this you could potentially deal with counters when damaging yourself (with poison or burn), but I don’t like those either:

1. Target the counter on yourself. This is generally a bad experience. You get hit by poison, which triggers a spiked shield and damages you again, which triggers a fire trap which burns you. Way too punishing and probably discourages shield and trap deck builds.
2. Always target your opponent. This is fun for the player, because your bad luck turns good, but as soon as it also happens for the enemy, it feels bad. Imagine you get a burn off but then you get “rewarded” by being hit by their spiked shield. You might have even chosen not to attack them head on because you knew their shield was spiked, and you still get bit.

So that’s why it’s set up this way. Counters only trigger when they hit comes directly from your opponent.