Judging by this line, user: namespace is defaulted to on. However, drafts have their own special variable. Currently enwiki, fawiki, hewiki, kowiki, ruwiki, and zhwiki have it on.

Thanks @Jdforrester-WMF . Not sure why we thought it was not possible - probably a mixup somewhere. Sorry for the confusion.

If there an option to disable VE for a subset of the namespace? Any other workarounds you're aware of?

I think it would still be good to have visual editor also there especially because of new users, so I'd like to understand better what's not working, so we can discuss that at the community. Is there a good summary of that?

In T159711#3077294, @Effeietsanders wrote:

Thanks @Jdforrester-WMF . Not sure why we thought it was not possible - probably a mixup somewhere. Sorry for the confusion.

No worries at all.

If there an option to disable VE for a subset of the namespace?

No. This code runs in a very high-profile part of the page load process, so we have to keep it as light-weight as possible (we don't want to slow down page loads for millions of readers just for benefit for thousands of editors). Adding code to make a decision based on more granularity (e.g. run a regex or do a DB look-up) would be way too expensive, sadly. :-(

Any other workarounds you're aware of?

One option, of which I'm not massively in favour but could work, would be if we were to switch the wiki into "Single Edit Tab" mode in always-wikitext mode (so the tab shown would always be "Edit"), and then have a default-on gadget that once the page had loaded re-wrote the target of the link to load VE in some circumstances. However, that'd be a massive hack, it'd be prone to breaking, it's not a supported configuration, and it might break things in some odd edge-cases (though I can't think of any off-hand).

I think it would still be good to have visual editor also there especially because of new users, so I'd like to understand better what's not working, so we can discuss that at the community. Is there a good summary of that?

To my understanding, the only reason that the visual editor is not enabled on the Dutch Wikipedia is at the request of the Dutch Wikipedia community. There are no technical barriers, though of course (as with all software) there are bugs, missing features, and areas we wish to improve. I don't think the Dutch community have a written-up explanation for why they – you! – do/do not want it, and what action is wanted (and from whom) to change that, if anything. Sorry. :-( I've created T161365: Enable VisualEditor by default for all users of the Dutch Wikipedia as a placeholder for hacking that discussion.

Change 570419 had a related patch set uploaded (by Jforrester; owner: Jforrester):
[operations/mediawiki-config@master] [nlwiki] Enable VisualEditor in the Project namespace

https://gerrit.wikimedia.org/r/570419

Change 570419 merged by jenkins-bot:
[operations/mediawiki-config@master] [nlwiki] Enable VisualEditor in the Project namespace

https://gerrit.wikimedia.org/r/570419

Mentioned in SAL (#wikimedia-operations) [2020-02-06T23:22:42Z] <jforrester@deploy1001> Synchronized wmf-config/InitialiseSettings.php: T159711 T161365 T164435 [nlwiki] Enable VisualEditor in the Project namespace (duration: 01m 08s)