I've been following these threads for a few days, and there are a lot of good theories and detective work!
I was just down in the Fashion District about 3 days before they found EL--it was a weird feeling to realize that I was so close and that she may have visted the Fashion District herself. I've also read Suzuki Koji's Dark Water, and the similarities are eerie! It's not the only scary roof thing that has happened in his books, either. Utter coincidence in my opinion, though.
To me, it's just not very plausible that EL would have voluntarily gone into that tank. In my youth I had a lot of mental problems and took a wide variety of psychiatric and illegal drugs, and I was much shyer and more submissive than Elisa's self-portrayal in her blogs. I never would have gone in that tank voluntarily, no matter how crazy or high I was. I would have fought to the death if someone tried to make me. So I think she was already dead. I certainly don't think she committed suicide...from what we know, she seems to have been on a bipolar up-swing. I think that if she crashed and wanted to commit suicide, she would have jumped from the roof--you only need a quick burst of courage to jump and you know you'll die very quickly.
I haven't seen anyone talk about this too much, but I've thought the simplest explanation for the choice of tank would be if she died on top of the maintenance building. Then nobody would have to carry her up any ladders at all, and the tank is right there. If a boy I was kind of interested in had asked me to go up there to check out the view and talk, I would have done it. If I was manic, I might also have gone with someone I wasn't interested in. Lots of unfascinating people seem fascinating to talk to when you're manic. It's a lot like being on speed (I speak from experience--a class of antidepressants induced bipolar III mania in me even though I'm not normally bipolar). I feel that I would have gone to get my glasses, but maybe not if I was more interested in the person than the view. She may have done completely different things than I would--this is just what I feel.
I found a book called Cause of Death: Forensic Files of a Medical Examiner on Google Books that sheds a little light on determining cause of death with a body that has been in water. I wanted to know if a medical examiner could definitely tell if EL had been strangled (the answer seems to be "not necessarily"). This link should go right to page 105-the story of Rachel Timmerman starts there:
http://books.google.com/books?id=EwOThAN8s08C&lpg=PP1&pg=PA105#v=onepage&q&f=false The gist of it was that the the ME needed to determine whether the victim was strangled/asphyxiated on Michigan state land or drowned after she was dumped in a federally-owned lake. This was an important distinction, because if her case was under federal jurisdiction the killer could get the death penalty. This was never truly determined, but the prosecutor was able to get the death penalty anyway (since overturned on a technicality).
I learned from this that MEs are amazingly good, but occasionally it's very difficult to determine the cause of death with total certainty. In this case, the examiner said that although he didn't find petechial hemorrhages, they may not occur if the victim was strangled with a towel over her throat (EL's killer could have used her hoodie for this). I read elsewhere in medical literature that the hyoid bone (contrary to popular belief) only breaks about a third of the time when someone is manually strangled. So, it could be...