If i had to just spit out a rough idea of possible alternatives:

• Only "unroll" comments if you had clicked on one deep in the thread, but leave all the threads "closed" at first. ie. only the immediate responses to the OP are visible, not sub responses

• Have a thin "gap block" that says "Unroll Responses" or whatever with an expansion arrow below each comment with an ongoing thread.

• Make the indent a lot more prominent (even at the expense of space for displaying the response

• Maximize the indent at maybe 3-4 deep, and then use dots or slashes before the first word as indication of how much further the response is in the thread? 🤔 (basic idea is after a certain depth, use something else to show derivation, rather than the indent)

• Another simple visual indicator could maybe be the darkness or brightness of the comment background. This could let you leave a thinner indentation, but use the background to visually indicate depth (ie. top comment in "dark mode" is 70% toward black, new response is 75% to black, next depth is 77.5%, next is 78.73% - ah la darkness halvening 😆)