To make data review easier it would be useful to add ability to show all entries with, for example, country code au and entries without countryCodes field.
Filtering can be either dynamic with some JS or static version of http://osmlab.github.io/name-suggestion-index/brands/ can be generated for every country
I plan to do it after automatic country matcher will process most of the data to avoid wasting human time on adding country restrictions that can be done automatically.
This doesn't really close the issue, but I did add countryCodes to the doc pages today:

Single page with all brands from each country unfortunately is too heavy for browsers that start lagging with 5MB of html, so there is a separate index for each country in my WIP.
I started thinking about keeping generated docs in a separate repository to reduce churn cause by regenerating it - and adding generated pages for each country is going to make it even worse.
For now I changed footer at bottom of each docs page to simply date - exact time is not too useful and it is causing all pages to change on each update.
And separate index for each country is also unreasonable - count of countries multiplied by count of supported tags is unreasonably large, it would generate thousands of .html pages.
The current static doc pages is something I threw together in a day or two.. It would be better to write an app that loads the dist/brands.json and dist/wikidata.json files and builds the documentation in client-side Javascript (and could do filtering and searching and other useful stuff).
I hoped that adding this will take hour or two and it worked but I forgot to check how many pages would be needed :)
I added this today! Try it out
https://osmlab.github.io/name-suggestion-index/index.html
looks like this.. You can filter on tag text or country code.

Most helpful comment
looks like this.. You can filter on tag text or country code.