My latest marine killed Cyberdemon with the BFG and got "He nuked himself on level 20." I didn't even have a nuke at that time. But I had found a nuke, two invulnerability globes and the entrance to Spider's Lair on level 18. Unsurprisingly, I nuked the Spider's Lair.
I noticed this bug was reported before, but there's another one with the same marine. At least I think it's a bug. I'm copying from mortem:
On level 11 he battled through a maze of rooms.
On level 12 he found hellish caves.
<b> He then ventured into the Halls of Carnage.</b>
On level 13 he found a hellish city.
<b> He then ventured into the Halls of Carnage.</b>
On level 14 he battled through a maze of rooms.
I'm not complaining that I got 2 BFGs and 4 supercharges. Just that I thing I shouldn't have.
Also, I saved on the stairs in the first Halls of Carnage, if that would help.
Version:win098, full