Change 232697 had a related patch set uploaded (by Mjbmr):
Disable watch category membership by default

https://gerrit.wikimedia.org/r/232697

Please explain why to disable watch category membership by default.

Related: T109672: [CatWatch] Preference for whether category changes affecting watched categories should trigger an email notification (separate from general enotifwatchlist)

We might also want to explore the idea of disabling it on specific wikis through #site-requests if it's not going to be done on core.

In T109633#1556869, @Aklapper wrote:

Please explain why to disable watch category membership by default.

On fr.wiktionary and other heavily categorized wikis the Recent Changes and Watchlists are flooded by modifications on category members. This new feature is certainly useful in some cases, but not to the point of having it by default for everyone in every project. Different projects have different needs.

I second the idea of Glaisher to disable this feature by default in a given project if its community requests it.

For the time being (copied from https://commons.wikimedia.org/w/index.php?title=Commons:Village_pump&oldid=169161650#Let.27s_try_a_little_FAQ ):

• To permanently "opt-out"/filter-out: Hide categorization of pages in Special:Preferences#mw-prefsection-watchlist
• To temporarily filter-out: Hide page categorization at "Watchlist options" in Special:Watchlist or Special:RecentChanges

The option "Hide categorization of pages" on Special:Preferences has disappeared both on Commons and fr.wiktionary : https://commons.wikimedia.org/w/index.php?diff=169170553

Maybe because I can't see what's behind the scene: T109638

In T109633#1558334, @Mjbmr wrote:

Maybe because I can't see what's behind the scene: T109638

The feature has been entirely removed for now. Once we're sure the issue is entirely mitigated I'll make the task public.

On zhwiki, as @hat600 requested, this feature results Special:Recentchanges as overflow, see https://zh.wikipedia.org/wiki/Wikipedia:互助客栈/技术#.E6.9C.80.E8.BF.91.E6.9B.B4.E6.94.B9.E5.92.8C.E7.9B.91.E8.A7.86.E5.88.97.E8.A1.A8.E5.B0.86.E6.98.BE.E7.A4.BA.E5.88.86.E7.B1.BB.E5.86.85.E7.9A.84.E9.A1.B5.E9.9D.A2.E5.8F.98.E5.8A.A8

I don't think we should revert T9148 completely. Only hide it by default like Wikidata edits.

The feature might be useful, but I think that hidding those from RecentChanges and Watchlists by default would be good.

In T109633#1575543, @Addshore wrote:

I don't think we want to disable by default for core.

And the reason?

Most of the justification for disabling the feature by default is that it is slightly annoying on large wikis where things are heavily categorized.
This does not cover the majority of wikis (thinking outside of the wikimedia world)

If this feature were to be disabled by default the majority of users of mediawiki would not even know that it exists.

The feature should be enabled by default but have a configuration option.
This option could then be switched on large heavily categorised wikis if those wikis do not wish to see such RC entries.