Sometimes blast causes the player to fightback even when /spellignore is on. I will be doing testing later on this to figure out how this occurs. It just costed me 8k gold and half my luck so I am reporting it finally.

I do seem to vaguely recall that Blast was considered a ranged attack as opposed to having a spell cast on you. Part of the get_hit od do_damage routines.

Assuming it is an attack, then spellignore does not have any effect.

That could be awkward if someone attacked you whilst you are surrounded by death traps.

I never looked at how to change this or whether it should be changed.

Also, given that Blast is a fighting attack, it does respond to using /fightback.

You can use /f to stop reacting to blast in regions with death spikes.