I created a commentary linkbase for US GAAP a while back. I started a similar commentary linkbase resource for IFRS-FULL (2016). Here is the 2017 IFRS-FULL taxonomy commentary. (This is the IFRSBOX commentary linkbase prototype.)
(I am doing that as part of my template creation exercise for IFRS which will expand my expert system to that reporting scheme.)
What something like the commentary linkbase does is allow you to add helpful commentary or other guidance or explanations to an XBRL taxonomy. It is just a label linkbase that uses a specific label role. You can see how the commentary shows up in a software tool in this graphic.
How much coding was required to get software to support this feature? Zero. Comes with XBRL; if software developers created their software correctly.
This XBRL instance makes use of the commentary linkbase. It also has a bunch of different labels, another very useful feature of XBRL. (Here is a screenshot of that.)
Imagine all the other documentation you could provide to make taxonomies even more useful! Got any ideas? Let me know.