It should now (finally) be resolved.

Thanks for informing me. I've procrastinated this a good while and am not that active currently. I'll look into it over the next week.

That does accurately describe the cases. I'm honestly not sure how to best approach to handle these cases are, but that "You can use this talk page to start a discussion with non-existent user" isn't it. I think just not displaying anything special from discussiontools would be fine, but perhaps a custom message like "This user does not exist on this wiki. You can check SUL to see if NAME is registered on other wikis.", "The page NAME does not exist. If you wish to create said page you can do so through the Artciel Wizard" or "The page NAME has previously been deleted. If you wish to discuss this issue contact the deleting administrator". Probably too specific for these to be the defaults though and significant localization is probably required.

Thanks Aklapper! No I've just been way to good at taking on additional tasks recently kind of making this one come lower in the pile. I've done some reading and I'll have a look at actually implementing it this week.

Great! I took care of MediaWiki:Coll-community book prefix.

@GhostInTheMachine Pages that would formerly be in the book namespace do not get special error messages by default since they are interpreted as new mainspace pages without history. This can be observed at Education program:Example which ones upon a time existed but the namespace has since been uninstalled.

Alright, just delete the page just before namespace deletion then. I can take care of moving the article to the proper name afterwards. Thanks for having a look!

Book talk has indeed been emptied as well and should be deleted as well. The matter of deleted pages in the book namespace was discussed at Wikipedia:Village pump (technical) § Implementation of book namespace deletion and there were no objections to those being lost, but if that is an obstacle to implementation I can move it over. As laid out at the discussion above the likelyhood of anything there being wanted is very low and any moving would run the risk of temporarily restoring copyright violations, BLP violations, PII or other material that definitely shouldn't be restored even for a short time. Doing the move properly and minimizing the time potentially very problematic content is visible would probably involve an admin bot which would take some time to get approved.

I mean I've said I would try contributing here and there's no better task than this to start with. Claimed, but unsure if I will finish quickly since I have to do a fair bit reading and setup first.

I would probably still agree with this if the integration would be simply disabled. But instead of that, the integration turns into support for a template, which is then transferred to other Wikipedia, where it is completely useless.

Just want to give this a big thumbs up. This is one of the features I miss most often and it would be great for dealing with polluted categories and awkward category trees such as Pages with long short descriptions and the categories for pages hitting template limits which are really badly polluted making them difficult to use (yes there are workarounds but doing it properly would be so much better).

Just want to give this a big thumbs up. This is one of the features I miss most often and it would be great for dealing with polluted categories and awkward category trees such as Pages with long short descriptions and the categories for pages hitting template limits which are really badly polluted making them difficult to use (yes there are workarounds but doing it properly would be so much better).