It's clearly not about guns. It's about believability. If you hit something (in this case a small fish) with a knife you'd expect it to die. Except that obviously isn't something that happens. The post in question essentially states "it was nice to run into fish with the seamoth and have them realistically die or have certain other fish bleed and die when hit with a knife but neither of those things happen in sub2 and it sucks"
