See also T336316.

It seems like it should be a relatively quick fix to get this to appear on the list of errors at Special:LintErrors. Is there anything that regular Wikipedia editors can do to move this ticket along?

Looking at the value of $wgLinterCategories, it seems it's probably because of the priority is set to "none", and as such, are "invisible" to users.

				"missing-end-tag-in-heading": {
					"dbid": 21,
					"enabled": true,
					"priority": "none",
					"has-name": true
				}

It's been that way since it's implementation in rELINTb9f1d478e2c9: Unclosed tags in article headings for T308398: Unclosed tags in parser content causes Vector 2022 skin cause display issues (strikethrough and italic tags) and should be flagged by linter.

Looking at https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Linter/+/914806 this is by design "for now", and to quote:

Note, at first we want this to be hidden. A conversation with the community is needed before making this high.

It's unclear which community this is (one specific wiki, all wikis?).

Currently, we don't seem to vary $wgLinterCategories by wiki, but we easily could (whether we should, is a different issue) this by wiki/similar in site config.

Interesting. I don't know why all of that process would be needed for a serious error that can leak into the rest of the page, including the TOC, the right-hand sidebar in Vector 2022, the title, and just about everything else on the page. See https://en.wikipedia.org/w/index.php?title=User:Robertgreer/sandbox/NYCB/Saratoga&oldid=962070708 for an example.

Change 979420 had a related patch set uploaded (by Sbailey; author: Sbailey):

[mediawiki/extensions/Linter@master] Enable "missing end tag in heading" error in LintErrors

https://gerrit.wikimedia.org/r/979420

Change 979420 merged by jenkins-bot:

[mediawiki/extensions/Linter@master] Enable "missing end tag in heading" error in LintErrors

https://gerrit.wikimedia.org/r/979420

Can this be marked as resolved? It appears on en:Special:LintErrors for me.

Yes, and thanks to the bug fixer!