It sounds like the point you want to make is that the implementation of bitfields is often buggy, therefore you should always avoid using them - does that sound right?

If so, I think that’s overly paranoid. The examples that are being given here are baroque usage that would immediately stand out in a code review - memory-mapped registers, conditional lvalues, volatile and atomic fields.

The point I wanted to make is that simple straightforward usage of bitfields, like the example I gave, works fine on any platform you’re likely to encounter.

There’s plenty of widely-used code out there that uses bitfields. I just did a code search to check that (the particular example I was thinking of comes from iOS) and found some in Clang - funnily enough, in its representation of lvalues!