Please notice that my idea in the previous post was not trying to convince anyone that write support should be included in the PEP. I completely understand the reasons of the authors/sponsors.
I was purely trying to reply to @barry’s question. My view is that yes, adding write support to the stdlib would influence whether or not tools include features (and given that writing TOML was already previously mentioned as brainstorm in the Packaging category, the existence of writing support can potentially also change future decisions regarding packaging and standards).
How relevant this is for the PEP or its acceptance is a completely different story. My view is that tomllib is useful/important even without writing support.
This is the discussion where TOML is mentioned: Python metadata format specification and implementation . I completely agree here that JSON would make more sense.
This is not the first time “writing TOML” shows up in the Packaging discussion (always as brainstorm). Before PEP 643 and PEP 621, there was some discussion about backends modifying pyproject.toml to remove the dynamic fields: PEP 621: round 3 (as we all know the idea was rejected and PEP 643 was crafted instead).