Change 552484 had a related patch set uploaded (by Ammarpad; owner: Ammarpad):
[mediawiki/core@master] Remove autogeneration of Deletion summary.

https://gerrit.wikimedia.org/r/552484

Note Wikidata explicitly overrided the behavior in T184025: Default deletion log for Wikidata items doesn't include label. The behavior in Wikidata should be preserved,

See https://www.wikidata.org/w/index.php?title=Special:Log/delete&offset=20191123102935&type=delete&user= for what I mean.

Usage check: no extensions known to CodeSearch use or override getAutoDeleteReason directly. ProofreadPage, Flow, Newsletter and Wikibase override Content::getTextForSummary (meaning the automatic summary is potentially more useful). ProofreadPage seems to only do it to get rid of the summary in some cases; Newsletter more or less preserves existing behavior (and in any case newsletters are a closely managed type of content so probably autosummaries are not very relevant in the first place); Flow displays the board ID (which seems pretty much useless, but I'm not that familiar with Flow so maybe I'm missing something).

For Wikidata the autosummary might be the only place which contains the human-readable name of the item (not Q-id) as Bugreporter points out (example) so I think that's a blocker to the patch in its current form. Maybe in the future Wikibase will be more intelligent about showing labels in logs, but for now this change should be blocked on reimplementing the behavior in Wikidata in some form, and also the generic mechanism of deletion autosummary (ie. the WikiPage/Article methods) should be kept.

2. The summary generates false contributor if the preceding revision is suppressed. Attributing attack/offensive content to other users is quite problematic (T24999: Article::generateReason returns wrong result when all users except one are hidden idling five years, unfixed)

Looking at the code, there seems to be another bug as well: it only checks the last 20 revisions and if those are all from the same user, it just assumes that that user is the only author. Both that and T24999 should be easy to fix though.

5. Offensive page creation edit summary cannot be hidden (except with suppression). Even if admin revision-deletes the specific edit summary, this autogenerated summary remains indefinitely in the page creation log for all users. (T230425: Page creation log should not display the content of deleted pages)

Admins who can delete or revision-delete the page can revision-delete the page creation log as well, but it's annoying extra work, and not obvious. That said, that issue is not related to deletion summaries and the patch as it is proposed now would not do anything to change it.

6. Creates inconsistency with other action pages. None of them generate automatic edit summary, even if the have similar field (cf. ?action=protect)

Automatic summaries are created on edit when a new page is created, an existing page blanked or reduced by more than 90%, or a redirect added/removed/changed. The behavior is a bit different though (the reason is not autofilled, instead the autosummary will be used when the reason is left empty).
Undo has a more similar prefilled autosummary, and revert also autogenerates a summary.

Somewhat related tasks:

• T14359: Deletion summary lengths problems
• the various tasks about displaying deletion reason to readers (e.g. T73578: Deletion log excerpt (mw-warning-with-logexcerpt) not shown when only curid given and page has been deleted, there is a similar one for reading deleted pages that I could not find) where displaying autogenerated offensive content that the admin forgot to remove is often brought up as a concern. (Although I guess even if that got fixed now, it wouldn't change things much given all the existing autosummaries.)
• T189045: Automatic edit summaries should not trigger edit summary pings (about edit summaries but probably applies to deletion logs as well?)

Somewhat opposed tasks:

• T11657: Add auto-summary to deletion of images
• T226824: Add custom summary for deleting broken redirects from Special:BrokenRedirects instead of default by MediaWiki
• T14554: Content on deletion page

Documentation note: if the feature gets kept, it would be nice if m:Help:Edit summary#Automatic summaries mentioned it.

AIUI the main reason for the deletion summary is that it includes the deletion template which includes the reason, so if the admin forgets to fill out manually there is still some clue left of why the page was deleted. (These days some wikis use deletion templates which include a delete button which pre-fills the summary; not sure how common this is though.)

I wonder if making the autosummary more clever would be a solution? E.g., use some naive regex to get the any templates that precede the wikitext and only put them in the autosummary.

This seems like a good idea to me, but we should actually check roughly what percentage of deletions is done with the default summary (and what percentage with empty summary).

My own experience is that on pl.wp there's a gadget (available for administrators only) with enhancements for the deletion page, which notably also always removes the autogenerated summary. It's called just "delete", and according to https://pl.wikipedia.org/wiki/Specjalna:GadgetUsage 85 active users use it (there are 98 administrators in total), but I'm not sure if we can trust these stats since it also reports 538 total users.

Archaeology: The deletion auto-summary seems to have been added in r1347.

This strikes me as something that could use some community input from communities that actually make use of the feature, particularly since it's reasonably easy for a community to disable it locally by setting exbeforeblank, excontentauthor, and excontent to "-".

In T239012#5689797, @matmarex wrote:

My own experience is that on pl.wp there's a gadget (available for administrators only) with enhancements for the deletion page, which notably also always removes the autogenerated summary. It's called just "delete", and according to https://pl.wikipedia.org/wiki/Specjalna:GadgetUsage 85 active users use it (there are 98 administrators in total), but I'm not sure if we can trust these stats since it also reports 538 total users.

On English Wikipedia, the auto-summary was removed since 2008: Remove default 'content was:...' and 'only contributor was:...' from deletion summary

I was curious, so I checked. I looked at 10 random moderately-large wikis (from s2).

4 of them have the message disabled:

• https://fi.wikipedia.org/wiki/Järjestelmäviesti:Excontent
• https://it.wikipedia.org/wiki/MediaWiki:Excontent
• https://sv.wikipedia.org/wiki/MediaWiki:Excontent
• https://zh.wikipedia.org/wiki/MediaWiki:Excontent

6 of them have it enabled, so I checked how often the default message is used (comparing the total number of deletions, to deletions with the default message):

(SQL queries used to make this table: P9737)

In all of these, default deletion messages are the minority, but on some it's ~1% and on some it's ~30% of deletions.

We've looked this over in CPT. Thanks to everyone who provided data.

Since communities can override this functionality on a per-wiki basis, and users can override this functionality on a per-delete basis, and some people find the autogenerated message useful, we think it makes sense to leave it intact. We're putting this feature request in the icebox unless further discussion brings about new perspectives.

Maybe add an option to disable it as a wg* variable or as a user preference? That way wikis/users who want to disable it can, without fully removing the feature for people who want it.

I agree with TerraCodes. @eprodromou what do you think?

Change 552484 abandoned by Ammarpad:
Remove autogeneration of Deletion summary.

https://gerrit.wikimedia.org/r/552484

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