It is be because all feed includes Lemmy.world, Lemmy.ml and beehaw.org. That means there will be duplicate posts retrieved from other instances. If there is a Lemmy.world post they would see it 3 times: one from original Lemmy.world version, one from Lemmy.ml and one from sh.itjust.works. Bit can only comment on sh.itjust.works version because they are not logged into Lemmy.world or Lemmy.ml
It is be because all feed includes Lemmy.world, Lemmy.ml and beehaw.org. That means there will be duplicate posts retrieved from other instances. If there is a Lemmy.world post they would see it 3 times: one from original Lemmy.world version, one from Lemmy.ml and one from sh.itjust.works. Bit can only comment on sh.itjust.works version because they are not logged into Lemmy.world or Lemmy.ml