No, that was just an example of a unexpectedly CPU-bound operation. My point was that you can't assume your Python program is not CPU-bound. Every time you have to do something non-trivial in Python, performance could become an issue.
From the perspective of a Python program, being memory bandwidth bound is the same as being CPU bound: you have the GIL, your process is in the running state in the OS, and is currently executing on a core.
(I assume you mean truly mean bandwidth between main memory and the processor, and not to disk.)
You are devoting multiple cores to parsing an individual user's BBcode?
This is your example of a real need to remove the GIL?