Fair enough. I think we have to be careful here - people do rely on how the "internal" aspects of virtual environments work, like it or not, and we've definitely broken people's code in the past as a result of taking a hardline "it's not documented, so it's not guaranteed" approach. (Disclaimer - we broke some of my code, so I'm not unbiased when I say the above ;-))

I take your point that this is a cross-platform issue, and as such would be worth putting in the `subprocess` documentation. When I looked, though, I couldn't really find anywhere that felt appropriate. I'll take a second look, but if you have any suggestions I'd appreciate it.

The bit that I *do* think is a venv gotcha is that it's entirely reasonable for a user to expect that if they run path\to\venv\Scripts\python.exe, then their Python script will be run by that executable. The redirector breaks that assumption, and while I'm fine with the idea that we don't want to document all of the details of the redirector, I *do* think we should document that you must not make that assumption.

How about this:

   The mechanism by which virtual enviroments are implemented means that
   you should not assume that the executable in the virtual environment
   is the one that will ultimately run your script. As a result, you
   should always use `sys.executable` to identify "this script's Python
   interpreter", as that is guaranteed to be set as you would expect.

I'm not completely happy with the above, but that's mostly because I'd rather just document how the process works (even if it's with a disclaimer "this is implementation detail and may change without notice"). But that's not my call to make, so I'll defer to you on that.