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

• Go to a talk page
• Click the "new section" tab
• Type #Test for the heading
• Fill in some random text for the message
• Save the edit
• Go to the history tab

What happens?:

• Edit summary is →‎#Test: new section
• Clicking on that does not jump you to the right section. Jumps you to the non-existent "Test" section instead of #Test section.

What should have happened instead?:

• Edit summary should be →‎##Test: new section
• Clicking on that should jump you to the #Test section.

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

Other information (browser name/version, screenshots, etc.):

• Was not able to reproduce with # in the middle of the section title. So this bug only occurs at the beginning.
• One might think there is no use case for starting a talk page heading with #. But it does happen sometimes in the wild. For example, https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)##Anchors_in_links_appear_to_be_broken_on_all_wikis,_all_skins and https://en.wikipedia.org/w/index.php?title=Wikipedia:Administrators%27_noticeboard&oldid=1106281408##WPWP_photo_contest_again