That makes it sound like a. you can never get an accurate stack trace, and 2. the stack traces you do get that are "inaccurate" are worthless.

I can't speak to every optimizing interpreter or compiler, but in the few that I've used, TCO doesn't do anything to code that doesn't have tail calls, so lots of the code has "accurate" stack traces.

And when it does perturb the stack trace, it does so in a very obvious way, it abbreviates the tail calls. Such stack traces no longer have a 1:1 mapping with the function "calls," but are still quite informative for debugging purposes. Not as informative as they would be if you turn TCO off just to debug that code, but informative enough that I rarely had to turn it off.