It seems to me that this would only make the situation worse (more posts in a single category), not better.
Almost all open-source projects have different “users” and “developers” mailing lists. So I don’t see why we shouldn’t do this on discuss.python.org also.
The main thing that I’m worried about is that non-core developers will be heard less. Either because core developers decide to discuss development on “Committers” or because core developers won’t check “Users” because it’s just a bunch of newbies asking questions.
Please don’t make it harder for non-core developers to get involved in Python development.