Back to main points----
It does appear that QR 778 and the tower both thought they were taxiing on S, not T from the radio transmissions. A landing aircraft was instructed to taxi behind QR on S as well.
This from the ever wise (i.e good analysis!) Airbubba (post #127 in original thread). Surprised there has been very little comment on this, either on this forum or in the report itself. (Yes I know, it is only preliminary, and they cannot speculate).
However, we all know it is VERY EASY to end up on the wrong taxiway, especially at unfamiliar airports with confusing signage and poor lighting (not saying this was the case at MIA though); happened many times before and will continue to happen.
Take another look at the airport chart; (sorry, not checked out on how to paste in here—so, go to Jepps)
Taxiing along T (thinking you are on S), you come to the end, with a left turn onto the runway. As somebody else has previously pointed out, it is easy to believe you are at the full length of the runway. Add the unfortunate nomenclature confusion of OPT "#T1" versus runway intersection "T1" and the holes start to line up. No heavy jet Captain would knowingly take off from such an intersection on a 12 hour long haul.
The EFB airport moving map is a great tool, but there are also traps; often, you need to "zoom in" to see detail, which means losing peripheral stuff, the Big Picture. Which is why it was my habit to have the hard copy 10-9 paper chart out on the clipboard as a backup, (even though that chart was available on the EFB and normally would be displayed by the other guy on his screen, and it was easy to switch back and forth between the two).
However, Sods Law says the EFB map will pack up just when you need it, (not a rare event). It also kept the old brain tuned in to basic chart reading while navigating around big airports, rather than relying solely on all that great electronic stuff.
Bottom line; we all make mistakes, and I do feel sorry for the guys .S—t does happen. But with 4 of you on the flight deck, there really are no excuses....