When I went into the darkroom last night I kept this thread in mind, and I printed one of the negatives on a roll of TMax 400 that I exposed on Christmas Eve last year. Due to the dim lighting, and no flash availability, I had to expose the film at 1600, two stops underexposed. In order to not ruin the film in airport X-ray machines, I processed in my father's darkroom, and used what was available, Paterson FX-39, at the 1:19 dilution, did a clip test, and processed while agitating every 4 minutes.
In the print, the shadows that are in focus all show detail and subtle variations from one part of the boy's garment to another. It's subtle, and wasn't picked up very well in the scan, but we all know those limitations. Scanning prints sucks.
Shot with a Leica M2 and a 35mm Nokton lens, at f/2 hand held at 1/8th of a second (incident light reading), which is why it isn't very sharp. Printed on Ilford Galerie G3 using Ethol LPD (replenished) developer, and toned in Moersch Carbon toner for deeper shadow impact, and improving highlight color.
To me this shows that at EI 1600 one can get great shadows, even in difficult lighting like this, which is a mix of candle light and incandescent/fluorescent bulbs. Given that it was incandescent lighting, the underexposure was probably more like an actual three stops, and not two.
I hope you find this useful, and as an example that by altering technique, much more can be had from the film.