I certainly agree that anyone who uses any substance has to be invest the time beforehand to research as much as possible, and be prepared before going into the experience.
I do not know of any toxic effects when mixing lsd and kratom, but as I mentioned: this only goes for small doses of each. A full-blown trip is best not mixed with anything unless one is highly experienced and is aiming for a specific level of shamanic experience. As for "deadly" do you know of any information that shows a correlation or is this more a retorical remark in terms of advice?
I dig Kratom precisely because I can handle it so well. Not sad if I don't have it for another year ;)

Hope you have been well my friend