This is related to bug 50872.
If you click the edit link on a section, then that section's heading is pre-populated in the edit summary when you save.
This does not work very well if you have turned on https://en.wikipedia.org/wiki/MediaWiki:Gadget-edittop.js ("Add an [edit] link for the lead section of a page") in the gadgets for your preferences. Editing the first (lead) section of the page gets a suggested edit summary that includes the first section heading on the page i.e., the section heading immediately underneath the section you were actually editing.
The link for 'edit source' says:
The link for 'edit' says:
https://en.wikipedia.org/w/index.php?title=User:WhatamIdoing&veaction=edit&vesection=1
The subsequent section editing links are all correct.
Version: unspecified
Severity: normal