Steps to replicate the issue (include links if applicable):

• I activate in my Preferences the numbering of sections to check right indentation -> https://www.mediawiki.org/wiki/Special:Preferences#mw-prefsection-gadgets:
• Heading Anchor: Adds section anchors to each wiki page heading. They become visible on hover. (Vector skin only)
• Auto-number headings
• i open page -> https://www.mediawiki.org/wiki/Help:Controlling_search_engine_indexing

What happens?:

• TOC is disabled there using NOTOC in the source, section numbering shows :

1 Software settings and robots.txt
    1.1 Software settings
    1.2 Robots.txt noindexing
2 NOINDEX magic word
    2.3 Individual pages
    2.4 Standard template noindexing
3 INDEX magic word
    3.5 Individual pages
    3.6 Current issues
4 Footnotes

What should have happened instead?:

• notice that headers == follow logical numbering, -> ok
• notice that headers === are cumulated, they do not restart from 1 each time we change the parent
• notice that once TOC is reenabled (deleting the tag line), the section numbering is correct :

1 Software settings and robots.txt
    1.1 Software settings
    1.2 Robots.txt noindexing
2 NOINDEX magic word
    2.1 Individual pages
    2.2 Standard template noindexing
3 INDEX magic word
    3.1 Individual pages
    3.2 Current issues
4 Footnotes

• so i ask section numbering to be realigned such as to display this last format and be independant from the presence of tag NOTOC

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.): Desktop + Vector skin.