sigma's not dead guys hear me out (BSD 109 SPOILERS)
when atsushi traded information via sigma's ability, his brain also needed time to figure out it, hence him passing out in anne's room. sigma this time went with the intention of using his ability to learn everything about dostoevsky, which the next pages show to be an INCREDIBLE amount of information.
its likely that fyodor knows of this caveat to sigma's ability and was banking on the fact that even if his ability doesn't work against gifted users, sigma would still be incapacitated for a while due to his ability.
every time that we've seen fyodor kill somone using his ability, there's been blood shown. this wasn't the case in the 109 scene, at least not visibly.
this still doesn't explain why fyodor would allow sigma to read him in the first place, but it could be that it was planned or even a bargain on dostoevsky's part to move things on skk wise and have chuuya take care of dazai without other interruptions
either way hes NOT dead (i hope PLEASEE) and surely next chapter they will be fine. right













