There are sooo many threads on oxtox. Here are a few of the more recent/interesting...
Likelihood of getting oxygen toxicity at 1.4 PPO
Oxygen Toxicity Limits & Symptoms
Thanks -- I'm embarrassed to say that I actually read through and posted in one of those threads -- I guess I didn't go through some of it in enough detail. If I am reading this one DAN study correctly, the answer to my question would appear to be that there are no confirmed recreational scuba deaths in the U.S. in the last 10 years clearly attributable to oxygen toxicity seizures when nitrox was used within MOD at PPO2 of 1.6 and within time exposure limits: DAN | Medical Frequently Asked Questions There was one fatality attributed to oxtox on 32% with a max depth of 160 feet. (Again, assuming I understood the study correctly.)
I recall in the other threads there was discussion of one or two possible seizures at lower levels. I also read the book "The Last Dive" and there was a tragic story in there of a diver who died used 39% down to 135 feet, so, again, outside accepted limits.
Some of this is repetitive, I guess, so I apologize for that. I guess we all want certain answers, but, of course everyone is different, and I am realizing our bodies are pretty fine-tuned to operate at 21% at sea level. Going back somewhat to the OP's original question, although I have no inherent desire to dive "deep" just to do it, there are some dives down towards the lower end of the recreational range that I'd like to do someday, and I frequently use pseudoephedrine to help clear, so gathering this type of information is helpful.