What does "better suited for [[mw:Developer hub]]" mean? Other pages linked from there? The Hub itself is so big and dense, it probably doesn't need more stuff.

The role of the Hub is to point to resources, in contrast to pages being tutorials. It should be as complete as possible. If it's not digestable then it needs some restructuring. So yeah it might get even more stuff but I'd hope that we can avoid that by removing some (likely existing) duplication.

IMO "done enough" with sorting out content (which also required edits on mw:Developer_hub, mw:Manual:Database_access, mw:Manual:Special_pages, mw:List_of_simple_extensions, mw:Annoying_little_bugs).

mw:How_to_become_a_MediaWiki_hacker now really focuses on MW core and MW extensions, as (surprise!) implied by its name, but...
Still want to move the now totally generic (not MW specific) "Suggested Reading" section to a better place as it affects all and any development on all and any projects, but wondering where. (After that, update the intro section on mw:Annoying_little_bugs accordingly which is also a mess of any and every project and not MW only.)

Killed the "General recommendations" section by moving it to the top of the page (scope clarification).